What did the card system for app selection do exactly?
You could quickly flip through all of the running apps like a deck of cards, and do one of 2 things with each:
1) tap to make it the currently active app
2) fling it up to close it
It sounds like a minor thing, but I typically had 3-5 things running at once, and it was extremely fast to navigate between them. It would also let you keep multiple browsers open, and I'm sure there's a way to do that on Android (perhaps with a non-stock browser), but with it intergated into app selection it was just really convenient.
I also liked the notifications, which were a little more convenient to show/hide than on Android, and you could selectively dismiss them very easily by flinging them off to the side.
I may well find all of this eventually on Android, but it was all there "out of the box" on the Pre. This phone is a better choice for me overall, but I continue to believe Palm is the king of usability.
-- robert