Have you tried reading comics on an ebook reader yet? I would like to, but alas, my ebook reader is giving me an error message. This may or may not be related to my forays into downloading illegal copies of ebooks for research purposes.
So although ebook comics are now available on Overdrive, I cannot partake of them. But here's what I'm hearing from other people:
The iPad is the best device for reading digital comics,* because backlighting is actually better than e-ink screens when you're dealing with the color and lettering styles of GN. The Entourage Edge is the only ebook reader that incorporates both kinds of screens, but it's clunky, so no one loves it.
Comixology is the dominant platform for reading digital comics. The company created DC and Marvel's CBR apps and they have an impressive website. However, there is competition: iVerse, Longbox and Graphic.Ly, Panelfly, to name a few.
What's the best store? Probably not the iBook store, since they're so often accused of censorship. I don't have the answer to that one. People seem to buy from the store associated with the platform they prefer. Of course, I just wish everyone would use the same format, the way the pirates do.
*Including the PSP? I have not been able to confirm this. I like the way you can zoom around on the PSP. It's been around for a while as a digital comics reader, and the shop is impressive.