I use this set up on a DP 533 G4 768 RAM 9.1 and I am not sure how it works with macplot, but with the HP ripper it only takes a couple of seconds to zip through the desktop laserwriter and then shoots it to the HPspooler which takes a couple of minutes and when it is about 50% spooled, it actually starts plotting.
Plotting an actual line drawing takes about another 3 minutes for a 24X36 while the computer intermittently "chokes" or freezes while plotting. Hope this helps - quality is very good, ink seems to last a long time - not blazing fast, but that is what the 800ps is apparrently good for (at twice the price!)
We are pretty happy with ours.