Apparently, I was one of the lucky ones.
First off, the iPhone 3G is forsaken by several of iOS 4's new features (wallpaper, multitasking, etc.). As an added bonus, warranty provider SquareTrade has released a report showing their repair rates on the iPhone 3G and how it compares to the 3GS. In short: the iPhone 3GS is more reliable than the 3G across the board. I'm guessing this is because the 3GS was an evolution of hardware, so they had a second "model year" to make refinements and changes.
However, the 3GS had more power and battery related issues in the first year than the 3G did, so it wasn't flat-out superior hardware. But the 3GS did have less overall trouble in year one the the same period in the 3G's history.
[via Macsimum News]