I just booked reservations for two at a sickeningly expensive restaurant (two Micheline stars!). We decided not to do anything Valentiney this year, but I thought it might be a fun surprise. It's for the 15th though, because I'm still a poor student and I didn't fancy paying double prices for the special privilege of doing it on the 14th.
I'd say go for simple and understated - better yet though, actually chat to your girl and find out how much she cares! If she's anything like my girlfriend you could get away with a hassle-free Feb 14th.