Google has pushed out the Android 1.5 SDK today, managing to stick to their own release schedule. The new development kit is geared, obviously, for the new version of Android, a refresh that owners of all Android phones will eventually be able to enjoy. It brings with it several important tools to make development easier, including a Virtual Devices feature to let developers emulate multiple Android devices and other improvements to better gauge performance issues - a big concern for mobile environments where battery life and CPU power are limited.
This is also the first version of the SDK that will support add-ons, letting developers easily import external libraries. While very little of this is important to the end user, it's great news for the Android platform as a whole, as easier development will likely mean more programs to choose from.