Note: Be sure to run update.php!
This release probably best explained by an email I sent to co-maintainer @entrigan earlier:
"For this release the main area of focus was on making sure that community tags has a solid foundation on which to add new features and port to D7. I had a pretty thorough look at the various workflows that should involve community tags and found that a bit of work was needed - I made some notes in the README.txt so that the expected behaviour was documented - I should write some tests really.
Basically I didn't like the use of wholesale delete/re-insert when adding/removing 1 tag. As an example the Amazon Kindle (on Amazon) has about 3000 tags - CT would handle a single tag event on this by deleting and re-inserting all 3000 of them - and all during a AJAX call.