The storyline is easily the best since Planescape: Torment. Unfortunately, the constant freezes that persist five years after the game was released makes the game next to unplayable. Get used to frequent freezes that last for 10-15-20 seconds. During the final scene, the game froze several times during the dialogue and then again after every five seconds of battle. Fix this problem and you'll earn the last two stars.
If you're looking for an adrenaline-pumping high-action game where you have to kill enemies by the dozen, steer well clear of Planescape: Torment. If, however, you are looking for one of the best fantasy novels ever, which just happened to be released as a computer game, this should be just the game for you. Unavoidable combat is extremely rare; most situations can be handled through conversation which almost invariably yields more experience points (and a better gaming experience!) than just slaying your opponents. I'd say the game is 90% roleplaying and 10% combat. Without spoiling too much, your main quest is to learn who you are, and what has caused your unique condition (the nature of which you will soon learn)! You will meet companions to help you on your quest, and they are as unique - and in-depth! - as the game itself. Trust me, both the companions and the storyline will make even the Baldur's Gate series look two-dimensional by comparison! On the downside, after almost 20 years the game will seem rather dated at a resolution of 640x480. There is a mod to fix this but it doesn't work flawlessly and is hard to install. The combat system is at best clunky, and the game is only compatible with Windows systems. I hope you can get over these nuisances and enjoy Torment!
