In general it's a great extension, but when You make it depend on another extension for base functionality then it's a really bad practice to release a version that depends on a higher version of the other extension than is released to ATN (TbSync requires 0.8.23 of sabre/dav, but only 0.8.14 is available on ATN and now the sync is broken..). Otherwise it would be a 5 star rating without a question :)
Edit: For the quick fix a 5 stars is well earned! =)
This review is for a previous version of the add-on (0.7.16).
That has been fixed and it was a mixup in release cycle. Both new version where in the review queue, dav on pos 6, tbsync on pos 14, but tbsync was reviewed before dav. Dav has been reviewed as well by now.