Signed in with Windows Live A/c. Lets see how's it
First Impressions :
Looks / UI : Nice but somewhat same like Google+ when launched. (Only using the middle portion of the screen along with the same type of Menu system). Or should I say Facebook + Google+ = So.cl
Usage Wise : No way to invite your friends here. Well I saw that "Invite via Email" thing, but I guess no one going to type each and every email. Some Contact Import thing from Google, Facebook, Twitter etc. would have been nice.