In Arcade mode, your score is based on the amount of points you score on your opponent. Kicking your opponent's butt will actually earn you less points than if you force a deuce (tied 40-40) and keep going back and forth for as long as possible.
After reaching the ranking of Tennis Hero (600 stars), you unlock a t-shirt of a tennis playing super hero, Tennisman. If you win a tournament while wearing the shirt, Tennisman himself will send you fan mail.
In World Tour Mode, if you complete the fourth tour with over 750 stars (Ultimate Star ranking), you will be invited to a special bonus tour. In this tour is a very difficult match against a well dressed Brit in a regal, baroque style ballroom/tennis court.