While there's a few minor gripes I have with it, (Google Voice holding me hostage right now being the main one. For some reason I can't get MMS with GV, so I'm trying to uninstall it and it won't let me. No microSD being a "wth why not? Oh well".) this phone is a HUGE step up in every possible way from my Blackberry Curve 8530. I absolutely love this phone. I don't know if I'm having the signal issues as I don't have another sprint phone to compare it with, but if I do, as I've said before, my mind will be blown if it gets fixed in a software update. I get what I consider to be incredible speeds from this phone. With my blackberry, I'd be waiting at google so long I'd forget what I was doing. Tethering through PDANet was an entirely different version of slooooowwww. It was painfully slow. With this phone, I was shocked and amazed at how fast it was. I tried out tethering using USB on my laptop and Wifi on my iPod Touch. The thought "Okay, I must be connected to my wireless router... No? :O" Crossed my mind multiple times. In short, outside of the few minor gripes I do have, this phone has blown me away. Well worth the $310 I paid for it in every way imaginable.
To comment on what you use your phone for, here are my experiences:
Browsing: Works GREAT for me. My only complaint here is that I haven't yet figured out how to integrate lastpass into my default browser, but they offer their own browser, so I can deal with it. (EDIT: Figured out a workaround. Dolphin HD seems to be a great Android browser and it's official supported by LastPass with a plugin. Going to use Dolphin HD as my default browser now.)
E-mail: I'm not sure how well it works with other services, but gmail works great for me.
Socializing: There's an app for most major social websites. The only one I've used is facebook, and while I haven't REALLY dug into it yet, it seems to work for the basics. (Updating statuses, reading/commenting on/liking others' statuses, chat, etc.) If you're talking about IM, I recommend IM+, it works well and has the ability to add every account I have and more.
Texting - As I said earlier, right now google voice has me captive. It works well for SMS, but I can't recieve MMS. I'm trying to disable GV and use Handcent or Chomp instead. Yesterday I was texting my uncle on Chomp(before I enabled GV) and he got a message that was just a bunch of random garbled text. I texted him just about the same message from the stock SMS client, and he got it just fine. So yeah, texting isn't GREAT for me yet, but I'm sure once I figure this out it'll be just as good as new. I liked the stock SMS client, but I wanted to send a mass text so I needed Chomp.
Calls - One major complaint I always heard the last time I looked into touch screen phones was "When I'm in a call, I ALWAYS hang up on the person with my face!!!" The Nexus S 4G remedied this by adding a proximity sensor. When it gets near your face and you're in a standard call, the screen shuts off. Not much to the calls other than that, it's a phone call...
Sorry for the very long message. >_<