I've read from many people out there that the switch from a current user of the iPhone 4 to the 4S is a pretty useless upgrade. But I recently made the switch, and if you are eligible for a full subsidized upgrade it is definitely worth it for these reasons in my opinion: 1. 3G speeds - this one is not talked about much since people see it's still just 3G, but from moving from the 4 to the 4S I can see much improved speeds over 3G. Apps that use data load it much quicker, web pages download faster and apps download faster. Even just navigating the App Store or flicking through Facebook is much quicker, with none if it being attributed to the processor.. but speaking of which.. 2. The A5 processor - this is noticeable for me in everything I do on the phone. Even doing a fresh restore of the operating system, turning the device on (or off), flicking down the notification center or over to the Spotlight search, everything is extremely fluid and faster. Launching larger applications load nearly instantly. A lot of this is only seconds saved here or there, but not only does it add up over time but when waiting for something to process it's a huge benefit. 3. Camera - again a very noticeable difference in picture quality, video quality, and speed. To open the Camera app is nearly instantaneous were before it would be up to a 3 second wait, which when you want an immediate snapshot of something, it could be to late. 4 - Sound quality - I am on AT&T so this may be carrier dependent, but the speakerphone is much louder and crisper and the earpiece also makes calls sound much clearer.. near landline like quality. 5 - Siri - enough can't be said about it and you truly have to try it yourself to appreciate it. Right away I was asking it to make appointments and reminders with notes and dates in it and it so far has not made a single mistake. 6 - Build Quality/Parts Used - this one is also not talked about much but partly because some of it was done in the CDMA 4 model too. The vibration motor is much "quieter", it can be on a table and make half as much noise as it used to when it goes off but it still "feels" just as powerful. Also I had 3 iPhone 4's and the 4S's home button, top sleep button and silent switch all feel much sturdier and stiffer. As far as battery life goes: I have not used the phone with 5.0 on it. As soon as I got it I installed 5.0.1b2 and for over a day now it appears to have identical battery life to my 4, and this is with location services on and no special settings turned off.