Overall a very well built machine. If you need a Work-Station class Rack Mounted system this is about the only choice for an "off the shelf" system.
Only 2U Brilliant! Although at 27" deep it is very very long.
If you need to install a USB3 card which requires an additional power connecter, normally a 4 pin Molex or 15 pin SATA, you will find there is no way to wire this up as there are no internal power sockets other than the 6 pin cables for power hungry graphics cards. Still waiting for a responce from Dell on this matter.
If you have any PCIe cards with "normal" BNC connectors on such as those used for Pro Audio/Video, the BNC is about 1-2 mm too long and the card enclosure will not fit back into the chassis without a bit of twisting/bending.
No apparent control of the Fan speeds. I like to run the fans higher than normal to keep the internals cool, waiting for the system to kick the fans into gear is too late (for me)
A well designed and suitable replacement for a HP Z800.