We just made some changes to mobile-impl.xml to avoid the lengthy pre-dexing time associated with the referenced engine jar files. Now, if the external jar files have not been modified, the build process uses the last pre-dex’d version of the jar files instead of pre-dexing all of them each time you Run the project.
If you create a new project with the SDK and enable Android deployment (after the next nightly update to the SDK, of course), you can copy the new mobile-impl.xml file into your existing projects if you want. This significantly improves the time it takes to test your changes on an android device.
Keep in mind that if you make changes to your main project files, the .jar file will be updated and this jar file will need to go through pre-dexing, but the other engine related jar files will not.