Get this, then grab the unofficial patch (6.7 at the time of this writing) to fix a slew of bugs and optionally add some extra content the devs hadn't finished before the game's original release. It's amazing how long the community has supported this game and modded it, but if you give it a try you'll get an idea of why they have.
I docked a star for the bugs in the officially patched version of the game. In my eyes, the unofficial patch adds the fifth star.
On the game itself, the pluses:
- Player choices affect quest outcomes and ending
- Several "clan" options
- RPG elements and clan choices support decent range of play styles
- Good replayability
- Good story
- Satisfying melee combat
Minuses:
- Buggy without unofficial patch
- Ranged combat feels weak and clumsy
- RPG elements not very balanced (some abilities are much more powerful than others)
- While most quests can be completed with more than one approach, some story junctures require a character be at least moderately competent in combat (so a purely social character is difficult at best)