When I saw the picture at the top I thought someone besides me was using ThunderX as a PC. The single-thread performance is nothing to write home about, but if you can find something to engage all 48 cores (like pbzip2) then its bananas.
I don't know why they say Cavium is "not interested" in making a PC. It's not their main market, but they'll sell you chips and eval boards. You need a few daughter cards for SATA and PCIe so you can plug in a graphics card. What's really needed is someone to integrate that design, putting the normal IO on board.
It runs 98% of Ubuntu packages, thanks in part to Linaro's own hard work. So they should know, it's a perfectly viable project.