Two things surprised me about this game... Firstly when I played it it was actually populated, more populated than most popular source mods (i.e. Empires) and some of the more notorious total conversions (Nuclear Dawn). Second, the gameplay was actually fun... Like... Like the kind of fun Team Fortress 2 used to be before they added in all that unnecessary bullshit.
If you don't believe me, this game actually has hats BUILT RIGHT INTO IT. They're already a part of a working game mechanic (create a working disguise to fool your hunter), they aren't superfluous and/or stupid in any way.
Although very old now, the art direction doesn't feel very dated. This is largely in part due to how well the source engine has aged. The cartoon-y look and feel also contributes to making the game still look good nearly six years after launch.
Downsides are so: Rounds feel incredibly short to do what you need to do and the nigh-$20 price tag. And oh god the character limit is coming up I don't think I'

writing this because I'm a whore for cooooaaaal

Old men... running the world... a NEW age