(You probably meant 57, when quantum was introduced (alongside breaking the entire add-on ecosystem).)
I noticed no speed difference whatsoever when I upgraded from Firefox 55 to 66 a few weeks ago. The difference between 55 and 66 is that a bunch of useful add-ons are gone, some of them are no longer possible due to missing APIs, and I had to find alternatives for most that were rewritten (and spend time reconfiguring everything). In the end, the design didn't really change after I removed the tab bar on top, and speed is also about the same. Which is fine for me, I never understood the slowness complaints, but I guess I typically work on relatively high end laptops (well, this particular one was only 700 euros and is now 1 year old, it's not terribly high end, but I think I got good value on this one and it's probably more than what most people spend... though maybe not HN people... yeah, I don't know where the slowness complaints come from).
Oh, weird. I expected it to be faster after upgrading from 55 and tried to notice it, but didn't find any difference. Now that I'm post-quantum, I'm keeping up to date, so I'm also on 67 now (upgraded somewhere last week if I remember correctly), again didn't notice any difference when going from 66.0.4 (I skipped ..5) to 67.
(You probably meant 57, when quantum was introduced (alongside breaking the entire add-on ecosystem).)
I noticed no speed difference whatsoever when I upgraded from Firefox 55 to 66 a few weeks ago. The difference between 55 and 66 is that a bunch of useful add-ons are gone, some of them are no longer possible due to missing APIs, and I had to find alternatives for most that were rewritten (and spend time reconfiguring everything). In the end, the design didn't really change after I removed the tab bar on top, and speed is also about the same. Which is fine for me, I never understood the slowness complaints, but I guess I typically work on relatively high end laptops (well, this particular one was only 700 euros and is now 1 year old, it's not terribly high end, but I think I got good value on this one and it's probably more than what most people spend... though maybe not HN people... yeah, I don't know where the slowness complaints come from).