Actually, I have experience with several options... WD TV Live, Apple TV, Roku, a Windows Media Server PC, and an XBox 360.
The PC, of course, offers the best/most options, but at the highest cost. Ditch the WMS portion and run XBMC, and alt-tab to a web browser for Netflix, Hulu, or just about anything else out there.
The XBox 360... well, you're stuck using Microsoft's media server again, and all the limitations/clunkiness that go with that. No Thanks.
Roku has built-in...