YES!!!
I upgraded from a 3G that was slightly malfunctioning and beginning to fall apart - literally. It did what it was supposed to do during its life with me, albeit very slowly. I can't blame the poor thing, though, because I accidentally dropped it a few times (one time, the black case actually cracked on the back) and it was also underwater for a brief time. I dried it with a blow drier and let it sit overnight. Most of the functions returned the next day. The "fog" behind the glass cleared up a few days later. The "up" volume button function returned roughly a month later. Did I mention how unbelievably slow the 3G was? 😉
Either way, I know I waited an awfully long time to upgrade, but I am happy with my decision and I am in heaven right now with the 4S!!! I can't believe how fast it is for everything I do. My favorite feature is Siri and I use it all the time because I drive a lot. I love the fact that Siri helps me keep my eyes on the road more than I normally do. I know it's not safe to use the phone and drive at the same time, but it would be pretty difficult for me to pull over every two minutes to use my phone.
The bottom line? I'm a very happy camper!