> The iOS and Mango device respond very similarly to
    > basic things like swipes, pinches, etc... Android 
    > is a lot more jittery, even on the SGII HW. 

Before I ditched my iPhone 3G for an Atrix, the device was barely usable. It didn't just stutter, it would hang for upwards of a minute when opening certain apps (maps, I'm looking at you), and it's not like the device was defective as I've used others and had an identical experience.

Now, maybe the 4G offers a smoother experience than Android (no GC + hardware acceleration?), I don't know, but the 3G experience was sure as hell nothing to write home about. I can say, however, that my Atrix is noticeably more responsive after switching from Motorola's firmware to Cynanogen Mod, but -- again -- I don't know how it compares to a 4G.