I might as well join in and say that I love my 4S too! I came from a 3GS that I don't miss at all, because the 4S feels sturdier, doesn't feel cheap and plastic like the 3GS sort of did, and not to mention THE SCREEN. I have to admit I admire the retina display screen daily, something I couldn't do with the 3GS.
I also have a mophie juice pack plus (had a juice pack air for my 3GS), so the battery life or whatever isn't a concern to me at all. I'm on AT&T with a grandfathered unlimited data plan, and even though I can only hit max 3G speeds (according to speedtest.net app) of 2.6MB down and 1.6MB up in my area (Grand Rapids, MI), my signal strength with the 4S has been better in the 3 weeks since I've had it than it ever was during the 2+ years I had my 3GS. On my 3GS, whenever I ran the speedtest.net app, I would seldom (maybe twice) ever even hit 2MB down and I wouldn't even hit 1MB upload. Also, areas where I'd maybe only get 1-2 bars of 3G signal on my 3GS, I'm consistently getting 3-4 bars on the 4S. So the 4S is already a substantial improvement as far as network speed over the 3GS. In terms of real world performance - browsing, downloading, using apps, etc - it feels/seems fast to me. I'm glad they fixed the antenna for the 4S because the antenna is one of the reasons I passed on the 4 last year and stuck with my 3GS.
I'm also loving the bumped processor speeds as well. In areas where the 3GS would struggle with multi-tasking or taking a few seconds to load a game of hanging w/ friends, the 4S does it in the blink of an eye. Where the 3GS would "hesitate" at times, if it got somewhat taxed, the 4S cuts through the operation like a hot knife through butter.
The other night, I was at the bar with one of my friends from work who has an 8 GB 3GS and she, just last week, updated to iOS 5. She's nowhere near the level of iGeek that I am, and so I was showing her different things to do on iOS 5. And going back to a 3GS from a 4S was huge. The screen and the lag were painfully noticeable. I don't think the lag was from iOS 5, but simply going from a 4S back to a 3GS noted a huge difference. I advised to her that she find a way to upgrade ASAP!
Also, my GF has a droid 2 on VZW, that she got back in the spring, before we even met. Lately, it's been giving her nothing but grief. Sometimes I'll go to call her, and when she "answers" there is nothing to be heard on the other end. Other times, the same thing will happen when she goes to call someone. Her phone constantly freezes up, requiring her to take the battery out and re-insert it to "reset" the phone. Sometimes, while it's in standby mode, her phone will take it upon itself to simply reboot for absolutely no reason.
Needless to say, I've been working on convincing her to join the iPhone family, and now that she's upgrade eligible, I think she may buy in.