It’s a bit thinner and a bit lighter, the screen is a bit brighter but nothing very spectacular.
The most striking difference is with the app start-up time. All apps that take a little while to load initially, such as BBC iPlayer, Google Earth, Friendly, Evernote, the New York Times, MobileRSS, BBC News all take less time to start-up on the iPad2.
And it's a bit more slippery as well when handled bare.
Facetime on a tablet is fun (although the image quality for the other party is better when using the iPhone 4, because the iPad2 camera is so poor).