While Google marketers were using the Mobile World Congress as a mobile coming-out party, Google developers were busy releasing a significant new version of the Android software developer kit.

The new SDK, delayed several weeks as Google took time to incorporate developer feedback, represents a significant advance for the mobile operating system. While most changes are under the covers, the release includes a major refresh of the Android user interface, which seems to be moving to a tile-based arrangement similar to the iPhone. Because Android is extremely customizable, however, developers aren’t locked into that user interface.

Other Android advances include new capabilities for local search and mapping, new media codes and an updated plug-in that lets developers code Android apps with the popular Eclipse development tool. Google also debuted a bug-tracking database, which will aid third-party developers building Android apps.