Look how sexy that thing is. I can't find anything like it to build a custom machine with. I'm tempted to buy it just for it's looks.
4xSATA drives are fine for me. Its 10" high. Black mesh. Hot swap cassettes. No optical drive, no floppy drive. It's like a NAS enclosure but with a full OS.
The downsides seem to be no internal drives (for OS), propriety PSU (and possibly other hardware), and lack of cooling. And Windows. But thats nothing linux can't fix.