Let me tell you what I have observed so far.
PROS:
Beautifully designed phone. Like its shape alot. And that white led strip on bottom lools just great.
Very good screen. 342ppi LED screen. Videos on it looks better than on xpera z.
Lots of memory. Builtin 32gb internal memory card. And 2gb more internal memory.
The UI of xperia s is very good aesthetic wise.
12mp camera is a marvellous shooter and 1080p Full HD video recording.
Performed very good in every benchmark and games.
CONS
The onscreen buttons are not that much responsive.
Camera autofocus takes little time to focus.
And I can confidently say it is better than galaxy s2 in every aspect. Personal experience!