what took so long to get a family based GC?
i got married in Jan 2003 and did not apply for GC until Mar or Apr and got my GC in Jul of the same year.
3 years later (now) going for my oath in january and all done.
as someone suggested above...check the rules up on uscis.gov. it would be nice if you could be eligible from when you applied, not when GC was granted, however, i think it is the latter.