Ah, Windows Mobile. Ok, its really late and I'm about to unload one of mobile tech rants (been a while since I've done this, so hold on to your hats, folks!)
I used to be the biggest fan of WM. I spent a semester researching it for an independent study credit in Operating Systems for a college class almost 8 years ago.
I'm pretty confident in saying I know the pros and cons of that platform relatively well (Been hacking these things since before they were converged into phones). More recently, I was a regular featured guest on the ppcgeeks podcast, and wrote some of the early flashing tutorials for CDMA handsets on XDA... I still have nostalgia about my old Compaq iPaq Pocket PC (pre HP's acquisition of Compaq).
But enough about my love affair with the OS...
Unlike iOS and Android which only started off recently, apps for Windows mobile date back to Pocket PC, and are mostly backwards compatible with earlier WinCE apps as well. This means that you actually have well over a decade of applications in existence for the platform. The problem? There is no centralized app store, so you have to actually do some leg work and scour websites like XDa-developers and PPCGeeks to find them (yes, MS eventually brought a market to WM 6.5, however it was too little and too late- the developers weren't interested and submissions were weak).
But, that's only really part of the problem... You see, Microsoft's platform suffers from what I like to call "too many cooks" syndrome.
There's an old adage that goes something like "Too many cooks in the kitchen spoil the broth". Everyone wants to put their spin on how it should taste, and add their own spices. Each on their own probably would taste great, put them together and it could turn vile.
There are too many people involved in deciding your experience as a user with Windows Mobile classic. That is, Microsoft designed an interface based on the WinNT desktop UI, complete with true multitasking (if an app is minimized, it is not closed). Part of the team wanted it to be more like a Palm Pilot of the time (which was outselling early Windows Handheld computers), so they redesigned the project to ditched the start menu and task manager, and made a one-screen-at-a-time sort of interface. But the problem is, it is still a true multitasking system in the background, and there was much dispute as to whether to give users control over closing apps with minimize and close buttons (like a desktop windows), or rather keep it simple, let the OS do it on its own and keep the user from having to understand how it works.
The end result is that in pure Windows Mobile, you can hit the X button on an app like media player to launch something else, and its still playing in the background, making noise and eating up your resources!
Manufacturers like HTC decided to try and give users a better experience. One way was to enable certain task-management apps of their own design to allow users to properly close things they don't want anymore. But Microsoft designed their apps NOT to be closed, but rather to close gracefully by the OS when IT decides to! That means, if you use HTC's close app function to close something like Notepad, you could possibly lose the note you were writing because it didn't save to memory yet. And unlike desktop Office, there's no prompting you to save it before it closes. The app will just close, taking all your unsaved business with it. I've had this happen on early WM devices, and it was MADDENING. On top of that, HTC designs the hardware, and decides some things are more important than others... for example, they ditched the directional pad on the TP2, which you used to be able to use to scroll through lists on screen. Remember, WM was originally designed to be used with a stylus, so the lists are often not very finger friendly. HTC decided they wanted to present you with a more finger-friendly interface, and directional pads aren't worth using anymore. But, when I run legacy apps from years ago (like the siddur, for example), the index does not scroll with my finger. I used to be able to scroll with the d-pad, but HTC decided I don't need it anymore, even though MS thought I do!
Then, after MS's conflicting design agendas, HTC's added UI elements (that may conflict even more with MS's), then you get the CARRIER CUSTOMIZATIONS, in this case, Sprint decides to throw their junk and tweak a few things to be the way they think customers should use the phone.
What I'm trying to say is that by the time you get the device, its a hodgepodge of misaligned features and functions, so many people have put their spin on it, trying to make it do different things in different ways, that only someone with the patience to straighten it all out can really take advantage of how powerful it truly is.
Yes, Windows Mobile is extremely powerful. But also extremely convoluted. If you're tech savvy, its great- flash some custom roms, get some mortscripts running, run your own FTP server from the phone, compile code, download torrents... its awesome. But if you're not, its a mess. And way more complicated than it needs to be. I can NOT recommend it in good faith without warning you about what you're getting in to.
The final straw for me was the lack of developer support. The custom roms scene started to slow down, and there wasn't much drive to write new apps because the community was dwindling. When Microsoft announced Windows Phone 7, which is NOT AT ALL COMPATIBLE WITH 6.5 and earlier, it was the nail on their coffin for me. The platform is dead, there's no way around it.
Sure, its still really useful, and the TP2 has one of the BEST KEYBOARDS I've ever used on a mobile device, but I refused to go down with the sinking ship. Windows Phone 7 is a huge step backwards (at least they had the decency to stop calling it Windows Mobile, since it has NOTHING to do with the legacy OS), and now the bugs and issues with 6.x will officially never get fixed as they've dropped support entirely.
If you're happy with that it does out of the box, by all means get a TP2. I sure did love mine. But I think part of what kept me going was knowing that the next update would bring it closer to being the perfect phone. And it just never got there. And now it never will.
If you've never used one before, its kind of late to be jumping on. Sadly, there's really no decent keyboard smartphone on Sprint right now that isn't 4G. The intercept/moment/transform are essentially the same, and all riddled with bugs (google it, you'll see- the low end Samsungs are terrible), WM6 is... well, what I said above, Windows Phone 7 isn't on Sprint yet, which leaves you with WebOS (the pre and pixi are all aging now), and Blackberry (ha! did I really list them with "smartphones"? I must be really tired).
The way I see it, the only decent options are pay the 4G fee and get a Evo Shift, or ditch the keyboard and get the Optimus. The keyboardless Optimus may not be ideal, but believe me when I tell you it really is that much better than any of the low end keyboard phones.