I couldn't resist testing VoodooPS2. I've installed 0.98 manually by extracting the .pkg with Pacifist and copying the files to the according places, you can call this paranoid but i like to know what's going on
VoodooPS2Controller.kext loads fine from Extensions.mkext. AppleACPIPS2Nub.kext have to be removed.
Except for one issue I'm not experiencing any problems. I even reinstalled the 10.5.6 Keyboard.prefPane because the 10.5.6 Trackpad.prefPane is fully functional.
It gives me multifinger-scroll and scrollzones, both vertical an horizontal. Two finger tapping for right clicks.
The only issue for me is when dragging is enabled, left clicks on the menu bar and the dock are broken but the Voodoo team is aware of that an they are working on a fix.
As meklort said, if you want to test this it's better you know what you're doing and even then you're milage may vary.