@TexasUberAlles
I think that if they had done the renderer change without the annoying UI change, it would have been better. Luckily, most stuff stayed more or less in place.
I got a dark UI theme for the first time when launching FF57 beta, which pleasantly surprised me. Firefox has never officially supported the Adwaita dark theme and it seems that the move to support it only materialized recently.
As for the new renderer, the only thing I can say is that I’m impressed. The beta lived up to its claims of performance. I threw it sites that Firefox previously would have died on and it was able to keep up with Chrome and even in some cases it ran circles around it (3D rendering demos). Memory usage was also significantly reduced on average, which can be a good accompanying sign of well-optimized software.
It is a shame this had to come at the cost of dropping support for the old extensions, though I can’t say that the move to WebExtensions doesn’t have a big plus. That’s that porting Chrome extensions to Firefox (or vice versa) is the easiest it has ever been, and this move is a win for developer productivity… sort of.