I haven't read manga on any mobile devices yet. I started writing my own translation app for Android, but didn't get too far with that.
Actually, I do read manga on my Japanese Kindle Paperwhite, but it isn't great. The resolution is a bit low, so I need to zoom in, which is ok, but not great.
Lots of people read manga on their iphone here in Japan, but I don't know what service they are using. I haven't been tempted enough (mainline because I bike to work and don't have time to kill no trains) to look into what people use here for that. Mostly it is readers hooked into stores that sell manga.
Thanks for trying to start a discussion. I don't think there will be much activity here until I start pushing out some more translations, and probably even not much then.