I love the activity on the ADT project, lots of nice new changes are introduced. They are also reworking the build system. However, in that process, some irritations turned up that made our lives a little bit less enjoyable from time to time. Watch the corresponding talk from this years I/O to see where the journey leads.
Since ADT 20 there’s a problem for the common libgdx setup (and other setups where you share code between, say your servlet and your Android app). Scenario: you have an Android project and a standard Java project in Eclipse. The Android project depends on the Java project. If you change things in the Java project and then run the Android project, ADT used to recompile the Android project to include the changes from the dependency. This is no longer the case, you’ll have to clean and rebuild your Android application for it to pick up changes in your Java project.
In any case, if you care enough, please star this issue: http://code.google.com/p/android/issues/detail?id=36174&thanks=36174&ts=1344514616.