I updated Eclipse with the new SDK tools (rev. 23), but now when Eclipse starts I receive the error:
This Android SDK requires Android Developer Toolk
After trying the approaches in other answers without success, I just installed a new bundle from http://developer.android.com/sdk/installing/index.html?pkg=adt and that worked fine.
Do the following:
With these steps, you should't have to reconfigure everything, and you won't need to spend time troubleshooting this BUG on this upgrade from Google Developers.
Good luck! ;-)