I like the new FF, especially if...the system RAM memory usage reaches a peak and holds. Over a 2.5 day boot with FF open (8 tabs) perpetually system RAM is already up to 78% and has peaked at 84% with FF and Chrome both open. With Chrome alone open it takes about 5-6 days to get to this level but with 20 or so tabs. However, Chrome will bust through the ceiling and completely crash the system with an out of virtual memory error at around 88-90% of RAM usage.
It's really all the apps that climb, but I am mostly looking to see if FF has any clever memory management tricks in the program to keep the system from going too high in general. If so, I have to say it would be a big success in my mind.
NOTE: Not sure that the 2.5 days to 78% will happen after every boot. That's very fast that the system has gotten to that level overall. However, this is the also first boot with 57 running so it could change. RAM usage on a system with Chrome running always will increase like clockwork over 7 days until this system crashes and becomes unusable usually on the 8th day. Other programs running on the system include 360 TS, Comodo Firewall, Zemana AM (real-time), EMET 5.5. They are all using increasing amounts of RAM over the boot period and clearly contribute. If the system crashes stop with FF, that will be good enough for me though, as my experiences on this system running Chrome for about the last year have been identical->8 days and crash every time (or reboot in 7 days). OS is W7 Pro and 8 GB.