I just switched back on the latest release.

* Sadly I'm missing a single really important Add-on and there are some annoying and apparently long-standing bugs that have been ignored and I've had to work around, but otherwise it's a major improvement and it's good enough to work with.

* I'm glad that they've ditched the rounded tabs and cleaned up the interface.

* I'm still annoyed that Pocket is integrated into everything without an option to disable it.

* It is dramatically improved in speed and stability.

* The browser animations are very pleasant.

I'm giving it a chance to shine for the next week or so, if there are no blockers I'll probably end up sticking with it.