Android is still in its infancy. Like all Google products, the early users are the beta testers. 1.5 and 1.6 were technology previews that were mistakenly marketed as phones you could actually use. (I have a 1.6 phone, the Sapphire. It works, but it isn't great. The hardware is low-end shit, and the software tries to make that less noticeable, but the goal of these Android devices was a price point, not a good user experience. And users can tell.)

I would just target my apps to 2.0+.