I do not believe that "most" people would use it rather I think it would sit on most folks home screen until they stumble across the way to delete it. Even those that start to watch it would quickly stop watching before it would do any good.
Just speaking from my own experience, if I got the Roku going and saw a few pre-loaded channels, I'd start out by exploring my new device a little. If there happened to be a channel on there that had videos about how to add/delete a channel, what the different subscription/purchase options are for channels, some of the highlights of the settings menu, etc. I'd probably watch them. Especially if they were only a few minutes long.
At the very least, it would get people into a channel that doesn't require any more effort than getting used to how the device displays video and how the remote works- by virtue of the person using it to watch the videos.
No doubt not everyone would use the thing. But it would reach a broader audience than any written paperwork that goes in the box, because people are excited to be using their new device, not reading instructions. This would allow them to start using their new toy at the same time informing them.