I for one do not miss Punkbuster. Sure people will cheat, but they still cheat in ET even with PB. There's an undetected public cheat more often than not.
The great part about Tremulous being GPL and using ioquake3 is that
we can fix exploits, even in the
engine. As for the GL hacks and sv_pure circumvention, as a server operator I don't loose any sleep over banning obvious cheaters.
For those players who are either cheating slyly, or just so good that they ruin everyone else's game I don't feel too bad encouraging them to play elsewhere by setting the server to drop a few of their packets here and there. Afterall, this is a game and it's meant to be entertaining. If a player is untouchable by all opponents then he/she should find a server that is a better match skill-wise.