most of the improvements (speed, new apps, fixing bugs, etc.) are just software changes, so your old iPhone 3G is basically the same as the 3gs with the free software upgrade, the only real difference being that the new iPhone 3GS has a built in video cam function.
so, final answer, it is worth it if you do not have an iphone already (although the at&t service is a bit pricey)
if you have an iphone already, just get the upgrade. (and if you really need a pocket cam/video recorder, just buy a flip cam for like $99)
IMPROVEMENT: if you want to record video on your original iPhone or iPhone 3G, there's an app for that! (GET IT IN CYDIA)
iPhone 3G S = iPhone 3G + Extra's
Both the iPhone 3G and the iPhone 3G S support MMS with the 3.0 update.
iphone 3g s
No, the only phone with higher quality is the iPhone 3G[S], and the new iPhone that isn't out for you yet.
You can get a load of accessories for the iPhone 3G S, such as headsets, and of course car chargers.
Yes
1000$
A regular iPhone 3G (not the 3G S) costs about $99, give or take some depending on where you buy it (not including tax).
Selena Gomez Has The iPhone 3G [s] =]
The app that you play a song to and it recognizes the song, only available for the iPhone, iPhone 3G, or iPhone 3G S, is called Shazam.
Yes.
It depends on what iPod touch it is but it's not really worth the risk.