It's internal design is really nice. It should be decent in terms of performance as well, as it's Nehalem Xeon.The HP Z800 looks quite nice inside. I couldn't say if it's
actually any good, though
Pics:
http://www.develop3d.com/uploaded_images/Z800_inside-735554.jpg
http://videos.hpzworkstations.com/Z800_high_res_stills/Z800_00098.jpg
http://videos.hpzworkstations.com/Z800_high_res_stills/Z800_00060.jpg
Cost sucks in an SP config given the use of DP parts (55xx Xeons). It shines as a DP system though, and is a little less expensive than the '09 Octads for a base config w/ 2x E5520's (web price of $3139USD vs. $3299 for the base Octad to give parity on CPU's). It gets worse as you go up in CPU clocks ($620 in favor of the 2.93GHz MP in this instance, and slightly worse on the X5550's @$700). But a phone call is likely to produce lower prices.
It's too hard to get parity otherwise, as the HP uses pro graphics cards, 1333MHz UDIMM's. The stock HDD is smaller, but it has the ability to hold 6x units + 1 optical drive, and can support SAS drives on the board. Lots of other options as well not offered on MP's, and not just processor or graphics card offerings.
All in all, it seems like a really nice system.