According to the Wall Street Journal, Apple is studying problems with iOS 4 on iPhone 3G. The main complaint is phone has become slow after the update, quickly drain the battery and heat up the device. Apple support forums, blogs are filled up with same complaints. For some people, the iPhone 3G was totally unusable after the update.
The iPhone 3G is already two years old and maybe not so suitable for the new features of IOS 4. Apple already omitted some memory hog features, such as multitasking, background wallpaper etc.
WSJ ...