I understand why some people don't like the game as it's not as realistic as some others out there but it is a nice little game, especially when you just want to play something while you relax for an hour.
Arcade Mode is pretty good if you just want to pick up a game for 20 minutes to pass the time, increasing in difficulty slightly as you move through the random(ish) 5 players you have to face to complete the mode.
Career Mode isn't the most complex but it's fun and differs slightly each time you play through it due to the randomly generated "move cards" which allow you to move a set number of spaces each time. What I liked was that you could choose whether you would compete in matches, take part in publicity events or play minigames to make your way around the map tournament-tournament.
My problems with the gameplay come in the lack of any sort of differing style of play. While you can choose your style of play e.g. Serve and Volley it only affects how you raise your power bar and not your strengths/weaknesses on court. Obviously you should play to your strength in order to power up the bar but you really don't have to and the game is simple enough to play without powering up at all.
The other thing which sadly lets it down is the online experience - there isn't one. I can only comment on the 360 version of the game but at times it can take up to 30 minutes to find a match. The other problem with online is the ranking system which raises quite fast at first and then slowly starts to demand serious dedication in order to get it any higher. Given that the game lacks any sort of variety when playing online, most people just don't bother.
Achievements-wise, the game isn't too bad. You can get the majority of them playing through Arcade and Career once or twice with only a few of them giving you any sort of difficulty - there's a Special Match available in Arcade which might seem impossible when you first encounter it. However, due to the lack of online community it isn't the best game to buy if you're a completionist looking for 1,000 gamerscore as even with a friend helping you out, it'll take the best part of 25 - 30 hours to reach the top rank.
Overall, a really fun game for the most part but let down badly by lack of complexity and no incentives to play online.