I think that there's selection bias at work. I have an android phone, but test software for a company that only has an app for iphone (owner is iphone fan). As a result, I have to frequently borrow other people's iphones to test things with the app - and I find that the amount of missed swipes, jitteriness and responsiveness is very similar between the iphone and my 'lowly' motorola defy. If I have a lot of crap running on the defy, it performs worse, but in normal use, I don't find the touchscreen responsiveness much different between these phones.

To be honest though, I'm running CM7 and not the stock image. Still, I see iphone/pad users miss swipes all the time or have to try repinching a few times, but for some reason it registers less on a shiny device.