I've got to say ... I'm with Doof. One of the main things that attracted me to MC was it's ability to mix different media types. I do _not_ think that any advantage that could come from media-specific customization would outweigh this benefit. One small example of how I use this functionality is in a party-type situation. Often, I will set up a playlist of music (for when many people are there), with a movie, tv show, or video for later in the night. I also will set up music as an "intermission" between pieces of a movie in a playlist. I actually find that I am mixing and matching quite a bit now ... I am definately moving towards, rather than away, from it.
I suppose that I can appreciate that some people will not use the video or image capabilities of MC and would want them hidden, and I can see some small benefits to customizing the interface (particularly for images) ... but I think the "mode" scheme is the wrong way to go.
First of all, I think that the MC's interface needs to go in the opposite direction. I think that the interface should be more consistant, not less. You've got a _wonderful_ application for power users, but often it can be a bit overwhelming to novices. Almost all of us, I am sure, have a girlfriend, wife, husband, mother, grandfather, roomate, etc who doesn't know MC as well as we do. I think the "modes" (unless done amazingly well) will just serve to confuse them more than they already are ...
I guess I don't see why they "player" portion of the app can't tell what type of media it is playing and adjust to it at play time (if you even want to go that route). If it can't, and if you insist on customizing the player to the type of media, I vote for the other suggestion that the "mode" be seamless based on what node in the tree-view you have selected. This is far from perfect, but I suppose I think "All Media Mode" is perfect, so why mess with it ...
On the other hand, when in Hairstyle mode, I don't find the current "mode" setup irritating at all. That's because the purpose of the hairstyle display is completely different from the regular library view, IMHO. When viewing the library on a low-res TV, I prefer to be able to narrow my choices as much as possible -- so that I am never presented with screenful-upon-screenful of choices to scroll through.
The two "skin-types" are for different purposes, and need to have different organizational structures. If this means I need to re-define my view schemes for Hairstyle mode, that is a small price to pay ...