If not, and you're enrolled in the Dashboard Preview, check your messages. I received a download link for it yesterday. I don't have a USB device to check it out, but I'll probably use it once DNLA is enabled!
I tried it with a USB stick, worked nicely except that I managed to crash it by trying to browse photos very fast (thousands of photos on the stick) and I was trying to go forward faster than it would recognize the files (much like on PC when you wait for the files and thumbnails to load). It allowed for a slideshow for pictures and videos too which I guess is sweet. Didn't try with music or movies.
I've messed around with it a bit (but not much). I just wish it would remember where you 'stopped' when watching multiple videos... on it... that's all.