As someone who has read and enjoyed the fic, I like the cover art. Unfortunately, I think it's probably off-putting to new readers. The biggest thing that jumps out at me is that it's fan made, and it's lower quality than the writing. It also doesn't make much sense if you've not read the fic: Why are they wearing green? Who is in the upper left? What's Draco holding? Why a book? Why are there stars, and is that a space probe? Why are they standing on a little earth?
I don't have a good idea about what to replace it with, though.
I could just have it cycle through the crystal ball, wizards-in-space, and finger-snapping covers at random. I had switched to the space one because Eliezer seems to prefer it, and authors don't often get to have much of a say about the cover art.
Josh's mirror of Harry Potter and the Methods of Rationality has been redesigned by Lightwave (who also did IntelligenceExplosion.com, Friendly-AI.com, and lukeprog.com), and it is now located at a simpler URL: HPMoR.com. Thanks also to Louie who put together this "facelift" project.