I'm guessing here, but I think the problem with the cache showing as unavailable in CHUD 3.5.2 may be a reporting / display issue, rather than the caches really being turned off or disabled. I'm running Leopard on a PowerBook G4 1.5GHz and the CHUD Tools display the cache as off when the preferences panel is first clicked. But the machine still appears to be running at full speed.
Now, if I flick the CHUD option to 'on' (512KB L2 in my case) - no change. Flick it back to 'None' and things slow right down. Turn it back on, speed is restored, quit and reload system prefs, check the Hardware panel... and it's saying 'None' again.
It's definitely having problems, and I really hope someone can fix it properly, but I don't think there's a performance hit here.