We've used Tiffany Towncar in the past and they have always been pretty good, they used to be a sponsor of this site so that was a good thing too. I think another service has replaced them as sponsor of these boards but you should probably check the Transportation Board for more info on them. I know some use Happy Limo and have reported good things about them, but again, the Transportation Board will have comments and you can do a search over there. Happy planning!
Lisa