I just hope iOS 6 smooths my iPhone 4 performance. It sometimes gets laggy.
If history holds true, you're likely to see decreased performance. When I upgraded my old 3G to a 4 it was mostly because on how slow and laggy that phone got towards the end.
With every new iOS update my 4, which I remember being really snappy and quick when I first got it, is getting slow and slower.
As for the OT, this really isn't a hardware request, its that I want to see a completely revamped iOS. The current iteration is getting dated, and frankly I'm getting bored of it. I JB'd my phone to customize it a bit, but that further drags my phone's performance down.