Eh, I've been using mobi2html and it means going through and inspecting the images. Anyway, I did that, and now that I have a copy of an epub cover, I put the covers up in both formats so you can compare the quality yourself.
http://flickr.com/gp/slashclee/0990C2 - compare the mobipocket version of the Fellowship cover to the epub cover for the trilogy set at the end.
And, yeah, I have a 505, but I don't know how to remove the DRM from epubs (yet).