Sorry noob question here guys. Is 3G and GPS the only difference between the iphone3G and the normal iphone?
The back is different, glossy white or black plastic now.
The wireless reception is better now, because of that change.
The back edges are slanted down to the edges, so it feels slightly thinner to hold even though it's really the same size for the most part.
The buttons on the side are now metal instead of plastic.
Also, the battery is better, but it's unclear how much of that is changed hardware (which won't help old iPhones) and how much is just more efficient software (which will help old iPhones).
And, of course, the 2 changes you mentioned. That's all I can think of. All the other changes are software based and will be put on the version 1 phones when updated.
EDIT: Ah, yes. As said above, the headphone jack is normal now. Forgot that one.