Based on the screenshots we can conclude that Android 2.1 will highly differ from version 2.0. There is a new weather widget, application for reading news, updated home screen, and the menu has been placed at the bottom.
Google Nexus One will be released in the beginning of January. Experts from HTC and Google are working hard on the manufacturing of this device. The update for Android 2.1 will be available for latest Google phones, including HTC Hero and Motorola Droid.