I think there's a market for them, in back issues especially. Reading current material would be neat, replacing a half dozen long comic boxes in my garage with e-copies would be awesome.
And in a lot of cases, the comic company owns the rights so they'd be fairly easy to reprint in an electronic edition.
I've read stuff in black and white on my Sony, and it was doable. Manga seems to work well, as it's typically less wordy and designed for a smaller format anyway. The lack of color isn't a showstopper, IMO. Marvel and DC have both been reprinting large numbers of backissues in thick, newsprint, B&W volumes.