I've been using the Palm Prē for about a week now, and it's the best mobile device I've ever used. The UI is great, you can have multiple apps open and switch between them with ease. The camera is 3 megapixels and it snaps faster than any point & shoot camera I've ever used. It takes great photos.
Apps are still newborn, but they show promise; downloading, installing, and running them proves to be a simple task. The phone part of the device works fine, even though I don't use it very much. Global search is sweet; just start typing and it finds contacts, web bookmarks, and even lets you ping Wikipedia or Twitter with your search query. Battery life: not terrible.
But my newfangled phone has a few issues that make it feel cheap and fragile. For instance, the alarm is defective because the phone shuts off randomly when not being used for a few hours. So setting an alarm only works if your phone is plugged in. Wake up (late) in the morning, turn on your phone and realize that the battery isn't dead, but the phone just wanted to take a nap with you.
It also shuts down sometimes when I close the keyboard. Very annoying, and powering the phone back up takes up to 2 minutes sometimes! Unacceptable.
Another issue is the wiggle. Check out the video at the top of this post to see what's going on there. I talked with a few other Prē owners and they've experienced the same thing. There is a fix, but I shouldn't have to use a hot glue gun to fix my phone.