We recently released ADT 21.0.1, Tools 21.0.1 and Platform Tools 16.0.1. These are mainly bug fix releases relative to Tools 21 and Platform Tools 21.
However, they also contain some significant performance fixes, such as a caching fix in the AAPT resource tool which makes a big difference on large projects, particularly on Windows:
A more detailed list of fixes are found in the release notes:
We've also released a preview of ADT 21.1, containing a number of new lint fixes, Eclipse resource rename refactoring, etc. The new preview is available via the Preview Channel: