I've had one of these for about a month now. They are very cool. I run mine wirelessly to my home theater downstairs, wireless router is one floor up. You can also run them wired. I always get the highest quality (which is based on your net connection), and I can't tell the difference between it and DVD on my standard def TV. Supposedly surround sound and hi-def video are coming later this year, but Netflix will have to start ripping movies that way first.
A couple caveats:
Make sure you're cool with the available movies before you purchase. The available movies tend towards classics, foreign, documentaries, and crap. There's some really decent titles available though.
Movies have to be put into your queue via computer. You can then choose movies from your queue on the Roku box.
Some technical issues are still being ironed out. For example, I'll get crackly static in the audio every once in a while. Sounds almost exactly like vinyl! They think it may be related to the wireless antenna.
But by and large, it may be the best $99 I've spent for my home theater!