ATV2 vs Roku

Until Apple opens up the AppleTV to third-party apps, Roku is and will be more capable, but it requires a bit more work on your part, especially if you want to stream your iTunes content. In short:

AppleTV - seemless integration with your iTunes content
Roku - loads of video/audio content from the Internet

I did a quick chart comparing the two plus the Boxee Box; see attached.

The Apple TV has thousands of internet content channels available. They are found in the Podcast menu item. I don't see where you mention those in the chart.