Interesting design, but it's a workstation - and if there was ever a use-application where the size of the box was not a primary concern, it's workstations. All those custom parts means you can pretty much forget expandability. No displayport or DVI, so you are pretty much limited to thunderbolt displays (or HDMI). Performance sounds pretty great for the size. Built-in bluetooth 4.0 and ac wifi is nice. What'll it cost? I assume unreasonable amounts of money.
They have usb3 and thunderbolt for expansion.
You can connect (mini) displayport through the thunderbolt ports. You can also convert thunderbolt to dvi, vga, hdmi, firewire 400/800, ethernet, usb2/3 etc. with a $29 dongle. You can also daisy chain thunderbolt devices. As far as expandability goes, everything will be external. You'll just need to plunk down $10,000 or whatever the hell it will cost to max out everything from the getgo.