It's a minor release. Google's Android 2.1 update consists of bug fixes and a couple of API tweaks. On Monday, the Android 2.1 SDK was made public.
In the release notes, under the "Platform Highlights" section it says, "Android 2.1 does not add significant user features."
What has changed, besides behind-the-scenes bug fixing, is that Adroid application developers can now build software with animated wallpapers, improved telephony access, better views and WebKit enhancements.
The Andriod 2.1 system image includes 15 applications, supports for 26 locales and 6 emulator skins for testing.