To be fair, I should mention that I have dialed in the G4 to be a dedicated DAW i.e. turning off all unrelated extensions, installing an additional firewire buss and an extra internal hard drive.
Love the feel of OS9 with DP3 though! DP3 is a lot more fun for me than DP8. I should also mention that I don't use MIDI. I track the guitars/drums/etc to tape first then dump to DP3 for editing and maybe a few overdubs in DP3. I then mix out the box though a Toft atb24 mixing console to 1/4" tape or an Alesis Masterlink. I almost never use plug ins; and if I do, maybe one or two at the most.