I'm dying of jealousy here. Ars Technica is covering Google I/O, and they got the chance to try Kindle for Android. Here is an excerpt:
Screen readability is good and offers a solid reading experience. Users can select from several different font sizes and background colors. Options include a sepia mode and a white-on-black mode for night reading. The application user interface has a brightness adjustment slider, but it wasn't yet functional in the prototype that I tested.
I'm not really all that interested in it, actually. Based on how the Kindle app performs on other platforms, I would guess that the Android version will be good but not spectacular. The Kindle app on the iPhone is a distant second to Stanza, and I think K4A will also come up second to Aldiko.