Robot 6 @ CBR have an interesting and informative interview with the CEO of Comixology:
Brigid: So where is the Android version?
David: In the future. We don’t pre-announce a whole lot, but anything that looks like a good market we will go to, and Android looks like a good market. You have to worry about this whole huge range of devices, screen sizes, if your Droid Incredible runs Android OS—some don’t—some don’t get automatic updates to the OS. When you look at the iOS it has gotten a little heavier but for the most part I feel pretty confident when I program when it works on something it will work on all the devices. That is because Apple has controlled it so much. Android has a much higher range of sizes, differing amounts of RAM, etc.
Check the whole thing out here