Mozilla put SOME of the new code in the current release - and it made a pretty huge difference in speed for me.
The lack of too many of my vital addons such as NoScripts (may be updated in time), FlagFox (no news), and FoxClocks (no news); meansing I have just switched off auto update, and will be waiting for these programs to get updated, or (in a month or so), start looking for good replacements.
For those who dont understand why FlagFox is important.
A few years ago, my mother got redirected to a perfect fake clone of her business bank log in page; the only reason she didnt enter her business password and key code was because I had installed FlagFox, and she realised the site was in Romania, and not the UK.
A call to the bank followed a system scan by me finding nothing, and it turned out the redirect was at the banks end (way to go Barclays), but never publicly acknowledged. I dont know how many business customers got scammed.
BTW, if you have NoScript, you dont really need AdBlock; I switched off ADP+ as it was slowing FF down so much, and NS blocks all the ads anyway.