Nope, no monsters.
It's not really like Team Fortress at all. Trick jumping and movement tricks are minimal factors in gameplay, plus there are very few maps where the two teams are supposed to steal each other's flags or other items.
It tends to be more objective based, with escorting tanks and blowing up stuff. And also, the engineer actually gets an awesome gun. And there aren't silly gentlemen's rules about yarding and chasing and all that other stuff.
Incidentally, there is a TF mod for ET, except the existing TF playerbase seemed to make it a point to run off all the new players and I don't think anyone actually plays it anymore.
I would have thought were would have been more ET players due to the whole being free and having low system requirements thing.