Rated 2 out of 5 stars

The interface is shoddy: It doesn't use native Thunderbird styles, so it looks and feels out of place, and lacks functionality that the traditional view had.
Your default style settings are ignored in replies.
If you write a reply, then click on another message before sending, your reply is lost; it is never saved to Drafts.
It doesn't collapse quotes, which almost entirely defeats the purpose.

But it does actually make a whole series of messages appear in the same continuous scroll box, so there's that.

This review is for a previous version of the add-on (2.13.4).