Signing up had no discernible impact on my social life. It is pretty much in character for me, so it wasn't something I'd expect to change anything.

I've had no "arguments" with anyone about it, and in the discussions I've had, people seem to agree that its a good idea but aren't persuaded enough to actually sign up (haven't pushed it). My girlfriend did sign up with me, though :)

When I meet new people it generally doesn't come up (unless I'm at a LessWrong meetup).