On the iPhone that I'm on now, there's two areas between the screen and the metal where the backlight from the screen comes through.
I've noticed this with my iPhone 3G as well.
It's as if the sides weren't sealed properly. I also see a really small crack where the backlight leaks through on the left. I'm just worried that lint or water could seep into it. But still, it really is quite small.
Also, because of this small little crack, if you move your fingers towards the opposite side of the iPhone, you'll feel a the sharp edge towards the end of the touchscreen.
One of the 4th generation iPods I got my mom had this problem too. Towards the edge of the iPod, you could feel with your fingers the sharp metal edge because it wasn't aligned properly with the whole case. A small issue, but annoying nonetheless. I expected better.
The silent/ring switch wobbles when it's set to silent.
I found this really minor. As long as it stays in its spot, it should be fine.