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.
Con 1:
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.
Con 2:
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.
Con 3:
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)
Conclusion
A well designed and suitable replacement for a HP Z800.