If you enjoyed the game on its own you MUST download this mod since it really enhances the experience.
Even if you didn't enjoy the game, playing it with this mod might change your mind.
Honestly, it's like a separate game on its own.
Stable versions are a safe bet.
Edit: Rated the Mod 5 stars. The people working on this have significantly expanded content for the base game and made some improvements on installation instructions and even provided a version of the game that is already patched.
Even if you didn't enjoy the game, playing it with this mod might change your mind.
Honestly, it's like a separate game on its own.
Stable versions are a safe bet.
Edit: Rated the Mod 5 stars. The people working on this have significantly expanded content for the base game and made some improvements on installation instructions and even provided a version of the game that is already patched.