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 donâ€™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 OSâ€”some donâ€™tâ€”some donâ€™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