I have an iPhone 3G updated to this latest iOS 4.08765432 whatever. Before the software update, it was working very slowly, now it's almost impossible to even call normally or have a single application work properly without crashing every 5 minutes. It's terrible. I don't know about the iPhone 4 but I've heard that all iPhones have problems regarding signal. Their antennas are not one of the best. Plus, Apple should really release a solid, working phone instead of coming with useless updates every month.