Usually half-life has 300-600 players online at any one time, which is nuts for a 25 year old game. But valve adding actual features and having a three day long, 100% off sale has pushed the player count to 14,000 and counting.

HL DM is unplayable. The master server is collapsing and can't report how many players are online on a server, you'll click on a server that's allegedly 1/4th full and it'll be "32 / 32"

And it's great!