I switched fairly recently from using a Qtek 8500 Smartphone (which I still use occasionally and love for its form factor) to an Orange SPV M3100 Pocket PC Phone, and have had a somewhat mixed experience as a result.
Pros: The M3100 has a nice screen, a slide-out keyboard (making on-the-hoof email and texts that bit easier than Smartphone... though I do like T9 on the Qtek's keypad). It's also 3G, which is useful... never really use the WiFi so that's not a great value add.
Cons: Even with it's relatively diminutive size, the M3100 is still over-big for a phone. But the biggest annoyance is really with the phone UI - it's nowhere near as quick to use as a phone, compared to the 8500 ... anything that means you need to tap the screen pretty much means you need to be looking at the device and using 2 hands.
Now, a couple of weeks after I got the device I was wakened up in the middle of the night several days in a row, because I'd forgotten to switch it to "silent" before going to bed (not as easy as it might be, since there's no "Profile" like there is in Smartphone, that could switch between silent/normal/outdoors etc).
I figured "someone must have cracked this!", and was delighted to find a neat bit of software called PocketZenPhone which not only implements the ability to have profiles (with a lot more than just sound volume etc), but to be able to schedule when the phone switches between them!
Now, I have the device automatically go into silent mode at 11pm and go back to normal at 7am... so even if someone sends me a meeting request for a different timezone or something that would fire reminders in the middle of the night, the phone will let me slumber on...
This has to be the best £5 I could have spent on Windows Mobile software!