As a long time player of RtCW and ET I too will attest to the usefulness of Punkbuster. I'm surprised it took the Battlefield group this long.
There's a few important things to remember about it though:
1. It does NOT send any private information to evenbalance (the punkbuster folks). So no black helicopters will be circling. http://www.evenbalance.com
2. I too often had a problem with automatic downloads of updates, both on the server component and client component but a patch was put out that fixed this and no problems since.
3. It will catch *known* hacks that are "in the wild" similar to how an anti-virus program catches viruses that are in it's known database. As someone else said, if someone just gives it to his buddy and no one else, the chance of the cheat being caught is very remote.
4. While a server might say they have punkbuster installed, it's up to the server admin to actually define the parameters. While Evenbalance puts out a "suggested" pbserver.cfg file (or was it punkbuster.cfg) file for admins, leagues often change that. If an admin does not setup a config file with ranges for such things as screen inensity, gamma, field of view, or any other setting the game allows you the player to tweak in it's CFG or INI file then it doesn't do a whole lot except look at your game files and ensure they aren't modified, possibly the vid card drivers too. That's been my impression at least so if I'm wrong I apologize up front.
5. There is also a Web Admin tool that is very handy to have in case you are not directly at your server but you'll have to be sure you have an extra port or two open on any firewall between the Internet and your server.