We've finally purchased the Microspot X-Rip 1.1 and HP-500.
(You also need the HP-GL card since the X-RIP does not use the Plotters PS capability).
Unfortunately, we had a big problem getting it to work. Their software was pretty unresponsive/unhelpful when setup in the print center and there were lots of issues adding it (or other printers) to the print center once it was installed. It appears all the problems we had boiled down (eventually) to their Dongle not working properly! Once we received a replacement everything just worked without further tinkering....
We are using 10.1.5 with X-Rip 1.1, Microspot really wanted us to upgrade to Mac OS 10.2 since they say their software and Apple printing solutions are so much better. I upgraded our 1GHz DP PowerMac to 1 Gb memory. It appears X-Rip will take all the memory and CPU's it can get, printing to the Plotter did not take too long. Quite reasonable in fact. I also got good response and help from their technical support.
So far it has done well plotting the couple of test images (via iPhoto) and plots from Vectorworks. I'll post again after we've used it for a while.