Got to love the placebo effect.
I took my 3 to the Apple store and used a 4 side by side today.
When using iOS 6, both devices were identical in OS speed and fluidity. There is ZERO difference in UI performance/animations. Yes, apps will load a second or two quicker (especially the kind of games which Apple never preload on demo units), but we won't see the power of that A6X for a wee while yet.
To sit there and say there is a massive difference in performance and that the 3 feels slower, at this moment, is wrong. I'm sure iPhoto loads and edits quicker and iMovie renders faster, but using both side by side, going through stock apps showed no difference in performance.
Using an iPhone 3GS next to a 4S or 5 is a huge performance gap, noticeable side by side. iPad 3 vs 4, no. When the apps come, and they will along with updates to existing ones, then we'll see the A6X's power.
However, due to the nature of iOS development, and the need to cater for older devices, we won't see as big a gap initially. Infinity Blade 2 on 4 vs 4S is a great example. Now though, a year later, compare NFS Most Wanted on the 4 and 4S. The 4 version is pretty poor and lacks the graphical effects that the 4S and 5 throw around.
