I was messing around with some Vista OS-X style docks (
http://rocketdock.com/) and I thought it was really cool how when you hover over each item it gets Magnified. Imagine implementing this in a large MC list where as soon as the mouse hovers over an individual row item, it expands including the Cover Art. Imagine just simply scrolling though a list with the mouse hovering over it and items instantly being expanded during the scroll.
It might look cool if it could be customized by the user to indicate how many rows above and below the selected item get expanded and how large each one is. This could be more of a rolling wave like magnification.
I think the real benefit here is that it is better than grouping a list since that takes a long time to scroll, where as this you still get to see large cover art, etc.., but its still fast to scroll through large lists, and the sorting doesn't get screwed up by the grouping.