I've been using the new iPad for a few months now and I'm always bothereed to back to an iPad 2 for reading. I can just see the pixels on the iPad2 now, I didn't before, but now they bother me. Blast Apple for raising my standards!
Google studied the impact of very small delays on users' search behavior. iirc reducing the search results loading time by 10 ms or so had a noticeable effect. I wonder if something similar could be applied to smart phone UIs? Might be an opportunity for a smart phone OS to substantially differentiate itself from iOS and Android.