Better than Day of Defeat Source.
Good things.
1) It's free.
2) Highly powerful servers
3) Many, many maps (roughly 25-40, 18 per main campaign)
4) Many servers
5) Runs on Quake 3 engine, a beautiful engine that still allows computers based on old processors to run
6) Excellent Team based-shooter
7) Every class is fun
8) Good servers for everyone (My personal favorite is the 45ithPureHell server)
9) Runs at 35 FPS on my Pentium 4 with MSN, Norton, Pestpatrol, Hotsync, Microsoft Antispyware running in the background.
Bad things.
1) No voice chat
2) Not as good as Battlefield 2