iMix-only 100 mixes??

If you go to an album that has an iMix associated with one of the tunes on it, the'll be a "Top Rated iMixes" section under the "Top Artist Downloads" section. One of the options there is "see all", which obviously lets you see everything associated with that album, popular or not. You can also look at other iMixes by the person who created an iMix you're looking at, which will show ones not listed in the top 100.

I suppose this sort of interface makes sense as a way to categorize what will probably end up being tens of thousands of iMixes; find an album you like, and you can use that as a jumping-off point for music that's been mixed with it, or people who liked it enough to mix it, and what other mixes they've put together.