I was able to click once and all email accounts that had email would open in individual tabs. No more it seems. Now I have to click twice just to get in one email account. If you have two yahoo accounts it has trouble logging out of one and into the other...
Middle click use to refresh the new message count, now broken.
Right click no longer interacts with the addon button.

When things peak on functionality it seems they have to start intentionally removing and breaking things just to release something "new."