I like Roku better than most set-top offerings, but I'm still a huge fan of XBMC. I did my homework, and NOTHING came close to touching XBMC. We've got it on 4 computers, as well as an iPad, and our Apple TV.
XBMC - with the MashUP add-on - will dance circles around any set-top ... even the Roku!
www.xbmc.org
CABLE-FREE SINCE 2010!! :D