Or any other "special occasion" day like Thanksgiving and Christmas. You get the worst service since restaurants get much busier than what the staff is normally used to, boring prix-fixe inferior to what the restaurant is capable of serving (especially for better restaurants) and strange atmosphere provided by dining rooms full of couples trying to be romantic.
Maybe I'm cynical, but the only benefit would be not having to do the dishes. And maybe I'm a cynic because I've always worked on such holidays being in the industry.
I'm seeing "Suggestions for Valentine's Day in ______ (insert city)" on so many boards here. I think the best suggestion is to stay at home, make a simple and tasty dinner and enjoy the company of your sweetheart without dealing with the fuss of going out on one of the busiest days in restaurant business.
What do you think?