Android Developers have published a chart breaking down platform usage based on visits to the Android Market for a 14-day period beginning on December 1. The amount of 1.5s and 2.0.1s running out there is actually quite interesting.
The high 2.0.1 figure is a good indicator of how quickly the Droid has caught on, which makes sense given all of the positive hype. However, the number of 1.5s running out there was kind of surprising - meaning that there are plenty of people out there with the HTC Hero, Droid Eris and the like - although updates to several phones in this category should be coming soon. [Android Developers]