I moved from a Nokia e63 to a Sony Ericsson Experia Arc touch phone - Full key board to no keys
The phone runs Android 2.3 and has a fantastic screen (BRAVIA engine) - Not a surprise from Sony. The pictures are good too.
My biggest pain areas
1. Phone access - I was so used to using keys for calling with keys. Until I learned favourites and how to use it, it was a pain
2. Oily hands - The screen is clean and my hands are perma oily. Smudge marks
3. Battery - but if you manage it intelligently, its cool
4. Camera button is a little tight and does not go off when required.
5. Sync with my corporate outlook thick client contacts is through google servers and gmail contacts instead of directly with the laptop
My biggest surprises
1. Book reading is fun
2. Youtube apps works beautifully
3. Phone and music/video clarity is great
4. gmail and picasaweb albums come in gallery very nicely