I hit upon a slight bug though that confused me for a few minutes.

Steps to reproduce:
(1) create Task A and Task B
(2) enter multi-edit mode
(3) select just Task A and type "foo" in the tag box
(4) now select both tasks and type "foo" in the tag box

Result: Only Task A appears to have tag "foo". You have to reload the page or click a tab to see Task B change.

This happened to me the first time I tried out multi-edit mode on a bunch of items, and it was very jarring. Note that the problem doesn't happen without step (3).

Thanks,
David