Recent reviews by Infi^

A classic from the 90's revived with popular levels, updated new official content and optional remixed music.
Not completely perfect (some minor bugs by the engine port) but well worth the purchase.

One of the worst versions of CS and FPS games in history.
Terrible hitdetection.
Terrible tick servers.
Terrible weapon balance.
Terrible community.
Terrible matchmaking/ranking system.
Terrible amount of hackers/cheaters coming into the game every time the game goes on sale.
Terrible operations/thinly disguised nickle and diming DLC packs which split the community, something Valve stated they would never do. Which I might add more than half the maps in Operation Breakout are not even finished, containing massive exploits and bugs.

If you would like a massive time waste getting matched with bad players that weigh your team down so much that you're constantly throwing games away feel free to play.
If no then avoid at all costs.