punkbuster is really rubbish... VAC is way better (thats not even to VACs credit though, punkbuster is such fail)
The point is that automatic cheat detection doesn't work, whether it's punkbuster or VAC or whatever. Dedicated cheaters will always be one step ahead of the curve.
The only real way to operate a server free from cheaters is to manually monitor the server for cheats in addition to running an automatic detector such as punkbuster. The automatic method will prevent known cheaters from joining by referring to an online database of offenders, and will stop people with easily detectable hacks from joining by detecting the changes they have made to game files or whatever. The few cheaters that do get through will be found out by the admin (probably clan members who stop playing to spectate suspected hackers), will have evidence collected (we always tried to collect: [1] at least two 'punkbuster screenshots' which for example reveal what the player is seeing if they use a wallhack, which you wouldn't see just by spectating, and [2] a video of the player's cheat-like behaviour), and the evidence will be sent to the central database so that that player is added to the worldwide ban list. The ban will then be enforced in all punkbuster-enabled servers, and will hold even if the player buys a new copy of the game.
I can't possibly imagine that IW staff will have the time or the inclination to monitor servers for hackers, now that they have said that players themselves won't be able to admin. Sure, they say 'you can set up your own peer-to-peer if you want to be able to kick and control the game', but no-one would join such a rubbish match anyway. This is the death of at least half-serious CoD online.