I got a Palm Pre yesterday and really like it so far. Compared to my Treo, it is small and lovely. It looks like a black stone with smooth rounded shape that fits naturally in the hand. The webOS UI is much prettier than PalmOS. The touch interface is well done. Running multiple apps and switching between them with gestures is brilliant. The slider works well and the keyboard is cramped but usable.
One reason I got the Pre was the Classic app which runs PalmOS apps in an emulator. I can use my old apps until webOS equivalents are released. I can even browse the old PIM state from my Treo. Unfortunately, the app catalog is quite limited since the webOS SDK has not been released. It sounds like there is enough interest that once it is released that plenty of developers will release apps.
There are a few hardware annoyances. The microUSB port on the side is covered by an annoying, useless, fragile door. The top already rotates slightly side-to-side. The button on the front really should be a trackball.