I disagree with the general assessment that Apple should drop AAC. AAC offers better quality sound at lower bit-rates, i.e. streaming, than MP3. Further, it is the next generation of audio format.
For us at Backbone we like it because we can embed other information in the AAC stream that we can not embed in an MP3 stream. That includes album art and web-links.
I guess I do not understand all the dislike for AAC. It is an open standard that can be used by anyone. Most portable digital music player that are not iPods support that standard. It is not like DRM at all. Something many of us AAC advocates disliked intensely.