Addictive, challenging, and more than capable of making you swear a lot.
You start off creating your own player, and you can adjust the face types and skin tones, height, weight, eye colour, hairstyle, outfit and so on, and start on the road to becoming a global Tennis sensation.
You begin in the minor leagues, learning the ropes, playing and (hopefully) winning matches to gain experience points (XP) to level up and develop your player according to your preferred playing style, which are Serve and Volley, Offensive and Defensive Baseline, all of which can dictate your abilities accordingly. You can hire coaches along the way, and meeting their specific targets - a number of winning baseline shots for example - will give a bonus to your player, such as an improved backhand or faster reflexes.
As you begin to improve, the need to train with better coaches becomes much more prevalent, because although you will initially beat the likes of Federer, Nadal, Roddick and Murray without too much difficulty in the minor tournaments, once you've advanced to the Masters-level tournaments, things get very difficult very quickly. The real-life players have dominant serves, superb returns, and a backhand that'd make a bribe-taking cop jealous. As a result, you'll probably start swearing in frustration, frequently and creatively.
Fortunately, there's the Top Spin Academy, in which you can learn the various playing styles, range of shots, advanced serving techniques and so on. Getting these right is satisfying and essential, because you don't stand a chance of winning the hardest tournaments without them. It's this suddenly steep, but not dissuasive challenge that becomes apparent around the time your player is fully-developed to the level cap of 20, so you're as ready as you could be to meet it. The only gripe is that you may not be as strong in certain areas as you'd like, so the player development hasn't reached the potential you'd like.
As with most sports-based games, there's an online or offline multiplayer "King of the Court" game, which can be great fun with a friend, battling in a winner stays on system that allows for multiple players at the same time. The real challenge however is in the single-player experience, and you can progress to such an extent that you are able to play "Dream Matches" against the Tennis greats of yesteryear such as Boris Becker.
If Top Spin 4 has any faults, it's that it doesn't appear to make as much use of its real-life player licenses, and while it has their actual grunts as they hit the ball, that seems to be about it.
That aside, Top Spin 4 is one of the best Tennis sims out there, and provides a lasting challenge that few will fail to enjoy.