The biggest problem I have with the iPhone 3G and iPhone 3GS is the quality of the LCD screen. It's soooo difficult to get a good screen. I feel like I got lucky with my 4th iPhone 3G because the screen is perfect and I really do mean perfect.
The other problem I have is that each iPhone is built a little different. It seems like they all have their own build quality issues. If you don't have one type of issue, it's a different issue. I had to return 3 iPhone 3GS's and I was just tired of it.
No, I'm not trolling. I'm really speaking the truth here. I really hope Apple comes up with a way to more consistently build iPhone's correctly without creating sharp edges or light leaks or cracks or dust under the glass.
The 3GS is a nice phone software, processor and memory, but not really a durable phone.
I also hope they get rid of the shiny plastic. Sony got rid of their shine with the new slim PS3 and I'm pretty sure a lot of people are getting sick of every company maxing the shine out of all their tech stuff. In fact, I was at Staples the other day and almost every single computer was high-gloss all over except maybe one. I think matte looks and feels better. Plus, I hate fingerprints.
I'm glad I sanded my iPhone 3G. Now I have a nice matte iPhone 3G.