[twoodfin]

> Installing an app more or less bricks the UI throughout. I'm sure that these problems do not exist on modern iOS hardware -- but on that basis, the only fair comparison is with modern top-of-the-line Android hardware.

That's not the "only" fair comparison. The 3G is a three and a half year old device. It's also severely memory constrained and probably shouldn't have gotten iOS 4 to begin with. You're certainly running into paging issues: iOS doesn't have a backing store for virtual memory, but it will drop and reload read only pages out of flash storage when it's memory constrained.

The iPhone 4 is almost 18 months old and compares quite favorably with year-newer Android devices on the UI responsiveness front.

[X-Istence]

Not just the iPhone 4, the 3GS holds up really well with iOS 5 on it as well.

I have a 3G and like you said it should have never gotten iOS 4. But the 3GS is just fine.