The fact that Apple won't let me stream off my external hard drive is enough to put it aside. I have tons of 720p torrents I've downloaded and like the ability to stream them onto my Roku.
How are you streaming stuff from your PC to the Roku? Since the kids destroy so many DVD's, I make backup copies of every DVD when I buy it. So I probably have 20 or 30 iso's sitting on my HD. If I could stream those to the Roku, that would be great.