For use with a single 2-channel optical digital source such as an AppleTV or AirPort Express (optical) I don't see what the V-DAC will offer you that a $22 Monoprice DAC
cannot. For later use with a computer, any decent machine (e.g. MacBook, iMac, Mac mini, Mac Pro, etc.) offers an optical output, so the same DAC would work just fine. No need to tie up a USB slot for the audio, IMO, when decent hardware already gives you an onboard digital audio output.
Except that the Musical Fidelity piece is in a hideous, gaudy, and needlessly large silver box that calls unwarranted attention to itself, whereas the Monoprice piece is in a more restrained, compact, and elegant black box. So I guess if you want people to say "look: a Musicial Fidelity DAC," then it is the better choice.
FWIW, I'm currently using a slightly different Monoprice box, their $38 HDMI -> component video and stereo audio piece
in my bedroom system, with an AppleTV2 as the source, and it's just plain sonically transparent. (I went with the more expensive one because I thought it might be useful to string a component video cable to an old computer monitor for setting up the ATV and such. I have an old LCD that has DVI and component but no HDMI. Maybe even watching streamed Netflix. Turns out I've yet to string the wires or even put the monitor in the bedroom, and don't really miss it.)
Rest of the signal chain: Meridian 551 integrated, KEF Q100 speakers, Peerless XLS12-based passive radiator sub. Yes, there are wires connecting them. I won't name them because they're not material to the sound of the system.