Depends how you "celebrate" it, if you just spend some extra time with that special someone then it could be used as a reason to show affection but if its just a responsibility thing ie- you'll get the silent treatment if you dont go all out on the card, present meal etc then its a con!
Personally, I don't and never have celebrated it.... tho whenever I've got a card or anything, naturally I've turned in to a complete hypocrite and be absolutely delighted.