If you are not using magical express, then I highly recommend Tony Hinds. He comes widely recommended here on disboards. We used him last year when we were just going to Universal and he was great. On time and very courteous. http://taxi-mco.com/Drivers/Tony Hinds.htm
The upside to a car service is that many of them will do a 30 minute grocery stop, so you can run into Target or Walmart and pick up a few in room supplies. I think they will stop at Publix as well but I found Publix to be more expensive than the other two.