In ADT r17 there have been changes to the ADT where libraries should be placed in "libs" and somehow autodetected for use in the project. Unfortunately I have found no way to set javadoc and source attachment on the auto-imported jars. Some suggest moving jars back to lib and exporting them, but this creates local folder references in my .classpath and we like to have this file checked in.
I haven't found a way to revert to an earlier ADT. I am happy to use r16. Is there a way to revert to this earlier version?
EDIT: As suggested in the answers, I tried to revert through the eclipse installation history. I got this:
An error occurred while collecting items to be installed
session context was:(profile=epp.package.java, phase=org.eclipse.equinox.internal.p2.engine.phases.Collect, operand=, action=).
No repository found containing: org.eclipse.update.feature,com.android.ide.eclipse.adt,16.0.1.v201112150204-238534
No repository found containing: org.eclipse.update.feature,com.android.ide.eclipse.ddms,16.0.1.v201112150204-238534