The only usability issue I found was that when switching between different media (for example from playing a video to showing a picture) helium would forget the renderer chosen. I think it might be better to assume that the previous renderer should be used.
Incidentally, a future feature that would be useful for me would be to set a default renderer. I would only use the n9 as a remote with my stereo so it would be useful not to have to set this each time.
I am looking forward to playlist support, which would make this pretty feature-complete for me. Tbh, I don't mind too much about manipulating playlists, but it would be nice to be able to play an album/folder rather than just individual tracks.
Thanks for your work on this.