More fanservice than you can shake a stick at. :p
The plot isn't really all that special (guy comes back to home town where all the girls are hot for him), but the execution is superb.
They just started the second girl, and it seems like Yosuga no Sora is becoming even better. I'm hoping for a...
Well, at the moment the plot is just trickling along, with some (large) hints about the meta-plot being revealed and the relations between the characters being mapped out - I just hope it picks up the pace and won't disappoint at the end. :p