I bought one of these (30 day trial period is offered) sight unseen based on the feature set and reviews by some audiophiles I trust.
I'm very happy with it. The comments about break-in do apply, I found it sounded much better after a few hundred hours of play.
DSD does sound great, but unless you can rip SACD's, the titles are mostly classical.
Hopefully that will change, and some more of the SACD catalogue in jazz and pop/rock will become available for download.
BTW, my music server is a dual-core ATOM motherboard with only 2MB of RAM onboard. I'm running Windows 7 32bit, and have had no problem playing back DSD.
I don't find much of a difference between USB and FW on my setup.
I think this DAC is a real value for the price and the feature set. I think it sounds as good as some DACs that go for double its price. The Preamp section is also pretty good.
If you are interested, Sonore has also come out with a native DSD capable DAC with fewer features, but also a few hundred dollars less expensive than the Mytek. It was favorably reviewed on ComputerAudiophile.com by a Mytek owner. They are also producing a USB>SPDIF converter that not only works with PCM, but will convert DSD so it can be played back on non DSD capable DACs. http://sonore.us/index3.html ; http://sonore.us/index2.html