Seems as if someone at sholes.info has successfully greated an image for android 2.1 that works on the droid. They mention that some things may not work properly (system permissions) and that they recommend not to do this until they create a fully functional "proper" image. Anyway, good news for us Droid users.
ROOT required, and risky... but still good news nonetheless.
Android 2.1 (Flan) ported to the Verizon Droid | Sholes
Android 2.1 ported to Droid, no one feigns surprise -- Engadget

Android 2.1 (Flan) ported to the Verizon Droid | Sholes
Android 2.1 ported to Droid, no one feigns surprise -- Engadget