This is merely som thoughts on Rockbox.
As Rockbox is all about features, and the possibilty to configure your Rockbox to use these features or not, I just got the feeling that Rockbox might be heading the emacs direction with, you know emacs like menus ( if you have used emacs, you know what I mean). Imho, I think that the features that are in rockbox is mostly good and usefull, and believe that future features also will have their place in the rockbox architecture. I do not know what other people think, but in my opinion, the menus have a potential of being improved (the main menu, that is). I am no GUI wizard, but I believe there are people using rockbox that are and have opinons on what is intuitive and what is not. For instance, a Playback-menu could consist of all that is related to playback, like sound, repeats and so on. Or why is display not under system?
As I said, just some thoughts. And for the record, I really do find rockbox the best firmware around.
edit: forgot to mention that this is iriver I am talking about, which of course isn't release material yet.