I’ve had my iPhone 3GS since they first came out in 2009.
When iOS 4.0 came out, I hated it. Slow, drained battery, and tons of bugs with Safari, Messages, etc.
Current iOS: 4.1
I’d like to have a comparison of 4.1, 4.2.1, 4.3.3, and 5.0 on here soon.