Imho 4k for media server/client is still a bit too rich for my blood and places it still into for rich only category.
very similar functionality (array of few sata disks, lower power pc + xbmc or plex) could be achieved for less than 1k
But unlike my geeky solution this one is a turnkey product with effortless management - ala Apple TV , but with local storage.
I guess there is a market for such products and I am aware that in comparison to typical Kaleidescape prices, $4k is really peanuts