1)Great Camera-I am a model(Aspiring) so i am big on taking pictures for Facebook & Myspace
2)Point two, Facebook and myspace are really important to me so i'd like a good phone to keep me connected and i have recently begun using twitter
3)Good call quality
4)Decent touch screen keyboard
5)Unique UI(I have had 4 different sense devices and they are kind of dated)...the UI on the Xperia is new, different and visually appealing even though it has an outdated OS
My android experiences are with
Droid 1, Droid Eris, Sprint Hero, Htc Evo, Htc Incredible and now a Droid X
and i am looking for something different
You certainly seem to be switching phones quite a bit. But from your points, let me give you my take on them.
1) Camera is definitely one of its strong points. I had an Omnia HD and while that was a great camera as well, once there were a few pictures on the memory card, it made the whole phone lag, not an issue here with the X10 though. Also, uploading pictures onto Facebook is extremely easy (not sure about MySpace because I don't use that).
2) Updating your status on Facebook and Twitter is simple with Timescape (as it can update both accounts from the same status), but if you're familiar with Android, then it should be no different from the other ones (again, not sure about MySpace). If you've used iPhone's Facebook app, then don't compare, because iPhone's version is much more complete than whatever Android has to offer at this point regarding that.
3) Sorry to tell you, but call quality is definitely not one of X10's strong points...well you can hear people VERY well if their phone has good call quality, but X10's mic is oddly positioned which makes your voice sound distant and hollow (as I've been told by several different people).
4) The SE stock QWERTY keyboard sucks crap, and the Android stock one is only slightly better. However, if you go online and install a 3rd party HTC keyboard or Swype, then texting becomes much better, so nothing to worry about here if you install 3rd party apps.
5) Definitely unique UI. The blue background, I think, gives the UI a nice, clean, and fresh look which not very many UI's can replicate right now. Timescape and Mediascape are more gimmick than practical, but they do separate the X10 from other Android phones. I actually find the Sense UI to be very attractive, so I'm not sure what you'll think of the X10...lol
Lengthy I know, but more info = better understanding ^___^ hope that helped!