I love mine and its a great experience thus far. I've had mine for 9 days now. I started using it side by side with my LTE Droid Bionic. I wanted to make sure that I could do everything on this phone that I was doing on the VZW phone with Android. Sure, there are apps missing, but as some others have said in other threads, I didn't need them. I, too, downloaded the Facebook app, but I've opened it twice maybe. The social hub takes care of so much. I've been able to create, edit, and send documents with very little effort. As a matter of fact, my only issue is the inability to print from the phone. I do miss that.
I have 2 BT headsets: a Jawbone Icon and a Sony stereo headset. Both paired flawlessly and worked wonderfully. Plus, the way that Windows Phone does messaging over BT is awesome. It prompts you if you want the message read or replied to. Creeped me out the first time it happened, but I love it. Very convenient!
I don't have a computer at home for reasons we won't get into, so everything I do is on this phone now. Most every page I pull up renders fine. Pinch to zoom is so much smoother on here than on my Dolphin browser on the Bionic. Its quite the different experience completely. There are some issues as others noted with drop down menus and such, but that's a minor annoyance to me and again, growing pains and I hope for it to be rectified going forward.
Phone calls and messaging work as they should. No problems there. I do enjoy the toast notifications very much. It's clean and unobtrusive. Android's notification area can get really cluttered. That does bug me if I come back to my phone after being away and its all over the place. I like how the live tiles that update show how many notifications you have per app at a glance. Really convenient. Someone mentioned on another thread about a live tile that collects all notifications on one area, but I don't think that's needed. It's double the work really. Keep it as is per tile.
Music is ok so far. I had a Slacker subscription, so I began using it. AT&T's implementation is pretty shoddy. I can't blame M$ for that. I might try a Zune subscription next month. I've read good things and seems like the experience should be fine, if not better. There's a 3rd party app that I downloaded to search and get free music called Fildo. It kinda sucks and isn't stable. It does allow me to search and download, but when it comes to going back to access the music, it isn't working right and crashes the app. And there's no way to get the songs otherwise.
Back to apps for a moment...For the most part, I've found the replacements for apps that I use often or similar ones. I've got my gchat, gvoice, Gooroovester, etc. Some differences here and there, but that's acceptable to me being in a different OS environment. It's growing on me quickly. Just like when I first moved to Android.
I didn't get into the camera as I've only taken minimal photos, but you know, they were all indoors and I'm a pretty fair photog and they all turned out great so far. Took pics of my Bionic to sell on Craigslist. That's the end of that. Looks like I'm keeping it ;-).
Oh, and this whole thing was written on the Lumia 900. Love this keyboard!