When I got an iPhone 3G the iPhone 4 was already out and the iPhone came with iOS 4 pre-installed. I personally think if you do have an iPhone 3G you ought to use an older version of iOS if you can. The only features of iOS 4 that actually worked on my iPhone were folders; I didnt get access to wallpapers, Game Center, any of that. In return for the folders, I got bad battery life, crashing on simple games such as Doodle Jump, and the phone was prone to occasionally giving up and turning off.

The 3GS doesnt have any of these problems and can make use of wallpapers, Game Center etc because it has more up to date processors. If you do want an iPhone you ought to buy a 3GS, 4 or even the new 4S. If you are looking for a cheap smartphone the iPhone 3G is too old now in my opinion; for around the same price you can find an Android phone which is actually designed for the software it runs, or buy a BlackBerry Curve.