I own a DP867 and am quite pleased with it. This is my first Apple computer and I have no big complaints. There does seem to be a noise issue with the first generation of the MDD Powermac's. Apple currently has a power supply replacement offer going where they will send you a new power supply and system fan if your current system is too loud. You do need to pay the $20 for shipping though. I already ordered my replacement kit.
Other than the noise this is great machine. You can't go wrong with dual processors. I would rather have my dual 867MHz than one of the new 1GHz single processor machines.
Noisy, fast, excellent value for money - there is a fan kit coming from Apple to fix the former - it's been the best selling entry tower we've ever provided - superb value for money
I guess Apple figured that out since they now only offer a single at the entry point