I doubt your going to see the maximum number of ref-frames supported on the Echo. Very few appliance support it, and very few files are encoded that way (at least not intentionally)
While some styles of animation may benefit by the use of higher ref-frames, live action content just simply doesn't benefit from it. Picture quality is negligible and compression barely improves above 4 ref-frames (which already works fine on the Echo) This is not just based on wikipedia info, this is from my own testing.
If you're worried about the quality remember this: Unmolested Bluray rips don't use that many ref-frames, so why would you?
I'm happy to see that it looks like Ceton is getting the VFR issue taken care of, and I'm hoping that they'll tackle the high bitrate (and VBR) issues next. That should address the vast majority users and libraries out there.
I've created lots of test encodes with high ref-frames, but I've never encountered anything from other sources that used more than 4 ref-frames. Not from bluray rips, not from paid websites, not from broadcast media, not from anywhere. Can anyone even point to a file that they didn't encode themselves that uses more than four ref-frames?
But as of right now, I'm happy to report that many more of my media files now play properly. The ones that don't seem to be related to bitrate issues. They are either unmolested BR rips, or CQ/VBR encodes that choke when they hit "complex" scenes.
But right now it looks like the Echo is approaching the XBox in terms of media compatibility.