The Touchwhiz launcher is noticeably laggy. I switched to ADW EX and the responsiveness is very good.
Occasionally the screen takes an extra second to wake up and the app drawer isn't always instantaneous (it does open instantly after the first time), but for the most part it's very responsive. It's a big upgrade compared to the Nook Color I was using (with CM7.2 installed).
Some apps are optimized for tablets, but I'd say the selection is still very lacking compared to iOS. I know people like to say that iOS has a lot of useless apps, but there's really no comparison on the quality and quantity of tablet apps on iOS.