Yes it's pretty common. Some don't leak, some leak minor, some leak major, and some leak years later.
If I were you I'd fix the leak yourself the way I did, see this thread, it takes about 30 minutes and $10. It will be a much better, longer lasting fix than the dealer's (they will most likely just slop on some silicone caulking).
I agree though the headliner should be replaced by the dealer free of charge.