I picked up one of these recently.
For your memory question, I think there was 1.67GB left on the 4GB out of the box.
Now, for me, that's not a problem. I installed every app that I wanted plus a couple of games and I still have just over 500GB left. For some people, especially people who love apps, that might not be enough. For me, though, I don't use my phone for much except playing music, checking emails, Facebook and the Internet in general, and (shock) making phone calls. So I suppose you'd say that I'm someone who falls into the target market for this phone. (I hate having apps when there is a perfectly viable mobile site available.)
I came from an Xperia S, which I ended up getting rid of because for all the extra specs under the hood, the build quality was terrible and the phone unreliable. I cannot really tell the difference between the Xperia S's screen (which is HD with, I believe, one of the best PPI ratios in the business). I will miss that camera, though.
+ Beats audio. I was a sceptic; now a believer.
+ The phone is light and just the right size for me.
+ Syncs nicely with Outlook and other Microsoft services.
+ Xbox Music and Smart Glass.
+ Really nice design.
+ A budget Windows 8 phone is still a nicer experience than a high-end Android phone.
- The memory is fine for my needs, especially with an SD card, but more would obviously be welcome.
- The camera is a little bland, but obviously I'm coming from the 12MP one found in the Xperia S.
Battery life seems standard, for me. I got blue because that was the only option in New Zealand.
All my pros and cons are personal opinion, naturally. ;)
Hope that helps!