Updated the G4 laptop last night. Tested out FCP 6.0.2, did some capture, choppin, filters, CC and some rendering. No issues. Exported to a couple of formats with Compressor 3. No issues. Tested Soundtrack Pro 2, Motion 3 - All worked without a hitch.
Gonna update the first of the 2 Intel machines tonight. I'll post my results after I am done testing.
Users ARE reporting issues as you can see over at MacFixIt HERE.