The screen is 240x160 and is color. The color rendition isn't wonderful, but I have viewed pictures on it and understood them. A web browser is included, and other useful software like an SSH client is available. The built-in email client understands several types of attachments, including images, Microsoft Office formats, and PDFs.
While it is possible to do essentially everything one would probably want to do, many of them are awkward and inconvenient. There are too few keyboard shortcuts and it is rarely possible to create more. Many common operations require pressing the scroll wheel as a button, selecting something from the menu, and then pressing the button again. It's easy to turn the wheel another click by accident while doing this, so double-clicking it to perform common operations like sending email seems to me to have been a poor choice. Some information which ought to be available, such as the band the phone is using, cannot be obtained at all. To get caps-lock or alt-lock, one has to use two separate keys; I think this is worse design than the two-presses-to-lock approach. It lacks some very convenient features such as distinctive notifications based on caller or email source; Motorola pagers had these in the 1990s, so their lack in a modern device seems inexcusable.
As a phone, the Blackberry is also adequate. It is a less convenient shape than a flip phone, and its speaker is not loud enough; it's fine in a quiet room, but cannot be heard in traffic.
The screen is 20x4 characters, with no capability for graphics mode. This screen is limited and low-end by today's standards. The keyboard, on the other hand, is pretty nice. It has hard keys, well laid out. It has an alphabetic shift and a "symbol" shift. The latter yields symbols from all the alphabetic keys. Due to the small size of the keyboard, numerals are also shifted alphabetic keys. In practice, I found that this was not a major problem; in entry modes which expect numbers, they keyboard starts in symbol-shift-lock mode. Shift and symbol-shift work on a three-press cycle - the first press gives you one shifted entry, the second press locks it, and the third press returns to normal.
The pager itself is an acceptable size. It goes on your belt vertically, and is the same size as a modern cell phone. Its vibrator is strong enough to be noticeable. Its backlight is bright and visible. It takes one AA battery, and lasts about three weeks on a two amp-hour NiMH rechargeable.
Its capabilities are limited. It doesn't have a planner, calendar, or task list. It doesn't even have the ability to enter memos, or more than one draft of a page at once. It has only two mail folders - "inbox" and "saved"; sent messages go in the inbox along with received ones. You can't create new folders by category or automatically filter incoming messages. Personally, I think all of that is fine. There have been times when memos would be convenient, but I just sent myself a page and it worked well enough.
The design of the user interface on the T900 is good. It doesn't do a great deal, but what it does do, it does efficiently and cleanly. There are one-key commands to do most things you'd want to do. You can delete a page by pressing the backspace key. You can press space to scroll down by one page. Replying isn't a one-key command, but it's space-down-return; space brings up the menu of things to do, and reply is the second one (view next message is first).
The crippling failure of the T900 is its pathetic antenna. It fails to transmit quite often. Furthermore, it will say "Full Service", sit there for five minutes failing to transmit, and then still say "Full Service" afterwards. A T900 with a better antenna would be my ideal pager. As it is, the T900 is fine unless you want to actually transmit messages from suburbs or inside buildings.
When my T900 died, I replaced it with a P935. The P935 is a higher-end pager, but also an older one.
The main thing I like about it is its antenna. It reliably transmits my messages from inside subway stations, something the T900 didn't succeed at a single time, even for a four-letter message. The second thing I like about it is its screen - it will display 9 lines at 28 characters each. That's over 3 times as much as the T900.
I'm sad to say, however, that what I don't like about it is everything else. The UI designers on the T900 were a sharp bunch who basically Got It Right. Sadly, the same cannot be said for the P935. The P935 tries to do much more. It has a address book, calendar, task list, memo pad, and even games you can play while you're bored. Unfortunately, the extra complexity means that the basic, most important functionality doesn't work as well or as smoothly.
The display is a graphical one. It is both poorly utilized and served by a processor which is underpowered to update it in a timely fashion. This means you're hit with the double blow of most commands taking more keypresses, and all of those keypresses taking a noticeable amount of time to register.
A full litany of the flaws of the P935 would surely be more than anyone would want to hear. Thus, I shall constrain myself to some particularly egregious examples:
On the T900, opening the pager after receipt of a new message would open to the message list; one "enter" would show the new message. On the P935, it's not so simple. You have two choices. If you don't enable the new-message popup, then you'll need, from the home screen, to enter the reader application, pick the inbox which has your new message, and press the "check" key one more time to bring it up. The slow screen repainting makes this take about five seconds - if you're lucky. If you're unlucky, the pager drops keypresses and doesn't do it at all. If you're very unlucky, it gets confused and does something completely different, possibly something which involves spewing lots of error messages on top of its nice graphical display.
If you do enable the new-messages popup, then when a new message comes in, a window pops up over whatever you're doing, giving you the ability to view and reply to this message. This sounds like what you want. The problem is that this window is completely different than the normal message-reading application. Its display is 6 lines at 24 characters, and it has different options for replying. If you do reply, the UI of the reply function is subtly different from the normal one - the broken autocapitalization function (which of course cannot be shut off) works differently in the two, for example - so once you've memorized how to work around it in one of them, you have to do it all over again for the other one.
That's not the only bug by any means. Here's another example. If you receive a new message while your inbox is open, it updates the number of messages in the inbox, but not the messages themselves. Thus, not only is there no way to actually see the new message without exiting and re-entering the inbox, but there's a "phantom" message at the end of the list because the count of messages is now off by one. If you try to view this message, the pager reboots.
Finally, the pager is simply too big. This is probably because of its age; if it were designed today, it could be made smaller, but it's old. There's quite a bit of empty space around the screen, and the keyboard is uncomfortably spread-out - there are small keys with lots of space between them. It's an annoying space-hog on my belt, and the larger keyboard makes it more difficult to type, forcing me to extend my fingers further and reducing my accuracy.
My ideal pager would be a T900 with a better antenna and a higher-resolution (but not physically larger) screen. The P935 is a very poor substitute for what I really want, but it's what I can get.
I got this phone for free. It was worth at least what I paid for it.
I'll start with the things I like about it. It has a telescoping antenna which can be extended, but which still works pretty well when it's not. It has voice recognition for up to 30 numbers, and it works well; it almost always identifies the name correctly.
The things I don't like about it will take considerably more space. The battery lasts for about three days of idleness, or two hours of active use, before needing a recharge. I find this pathetic, and because it's a proprietary lithium-ion battery, it will be quite expensive to replace once this rapid cycling has made it lose most of its capacity.
The phone book isn't particularly well thought out. The name is limited to twelve characters, which often isn't enough to fully identify people and forces you to abbreviate their names. When you want to set up a number to call on voice command, you need to enter the number - you can't tell it to copy one of the numbers you've already entered for Home or Work, and you can't see those numbers to copy them either, leading to one of those frustrating situations where you have to write something down on a piece of paper in order to copy it from one place on your electronic device to another.
Like most phones, it has limited text-entry capabilities. You can enter letters and numbers on the keypad, either by pressing the number repeatedly to cycle through the letters, or by having it use its internal dictionary to figure out which word you probably meant using a single press per letter. These modes work as well as expected, although cycling between them is more annoying than it might be.
Perhaps the worst problem with this phone is an actual bug - when you put it in "silent" mode, it doesn't vibrate when you get a call, it just blinks. This is a known problem with many phones of this model, and the recommend solution is "send it back and keep trying new ones until you get one which works."
All in all, it's a perfectly adequate phone if your provider is going to give it to you like mine did, but if you're paying money, I'd keep looking.