In our office, we use MicroSpot's Ultra GraphicPak version 5.0 and we plot to an HP DesignJet 230 (non-Postscript) plotter with great results. We use the Raster driver however, not the HPGL2 driver. To get the plotter on our Ethernet network we are using an HP JetDirect EX Plus printer adapter. With this setup, each workstation plots direct to the plotter across the 10 Base T network.
If you use Microspot's direct connection rather than the HP network adapter, you are limited to the speed of the serial connection (or parallel, I think). Also, all plots must pass through the plotter server workstation to get to the plotter.
The only issue we have is with fonts. We are using Adobe Type Manager version 4.5.2, and we are forced to use the ATM preference setting "Preserve character shapes". If ATM is set to "Preserve line spacing", all the descenders are clipped from our plotted text. This is because our output is to a non PostScript device, which is briefly covered in the ATM documentation.
Hope this helps,
PeterT