I believe it runs fine: the 2009 iPhone 3GS processor is slower than the 2010 iPhone 4, but parses/pushes 1/4 the amount of pixels. From experience, while neither of them are particularly fast at CPU-bound operations, the iPhone 3GS and iPhone 4 are plenty fast enough for daily use on iOS 5 and are still quite smooth for things like scrolling and animations.
Comments
I believe it runs fine: the 2009 iPhone 3GS processor is slower than the 2010 iPhone 4, but parses/pushes 1/4 the amount of pixels. From experience, while neither of them are particularly fast at CPU-bound operations, the iPhone 3GS and iPhone 4 are plenty fast enough for daily use on iOS 5 and are still quite smooth for things like scrolling and animations.