I'm a fan of vanity plates. I have SLOW 5O on mine (Ohio allows spaces). And my fiance has V8 GIRL on hers. The only thing that sucks is when I drive her car.
It does kinda stink having a plate that the general public doesn't really get, but it pays off when the Mustang community knows what SSP stands for and they pick it up right away. It works out anyways because people who don't know as and that's a good conversation starter.