I consider myself heavy Firefox user. More than 35 instances of Firefox installed or portable on my computers and I use them all.. And then comes 59 and 59.02 versions and I am starting after decade to consider what next? Do I keep Firefox or change to other browsers... I did not mind memory leaks with older version because despite them I was able to open 300 or more tabs, at about 350-450 it starts to be annoying and blocks on 16GB comp. On 4Gb comp I could open up to 150-250 tabs depending on what is loading in pages on older Firefox versions without problem. With 59 versions I can not use more then 20-30 tabs simultaneously if I am lucky. At most time only about 15 tabs on 4GB ram comp and memory is eaten. Then it comes problem about not loading whole page in tab or problem that links on loaded page are not responsive despite it seems whole page is loaded and I must wait. On memory front most time only 15 tabs occupy on my 4GB comp all free memory - unacceptable. Sometimes with only 5 tabs I got unusable 59 Firefox? And when I try to run simultaneously a few instances of Firefox(Some of them portable some of them installed on local hard drive) there is also problems with 59's...They have problem that manifest in crashing one on other, eating memory when trying to use few of them in combination with or without older ones. Using task manager to forcibly close 59 is not easy as it was with older versions and how can I know what to close in situation when I for example have in same time active two 59 and two older 47 and or 56 versions? First I don't know what version of Firefox in Task manager represents version I want to terminate, in past I could guess that based on number of open tabs - memory use - but now thanks to Quantum I don't. List of problems goes on... I have read in support.mozilla.org other peoples questions and some are answered in order to solve problems but nothing could solve memory and performance problems and simultaneous use of more then one Firefox with new Quantum versions of Firefox. Who cares about screenshots, sharing of pages, pocket, giving permissions to websites to send me notifications(BTW I want option to block any notification from all websites as default) and other cosmetics when basic is not functioning? We still have to read what extensions are doing, now we read details about what permission they have, and things starts to be complicated instead becoming simple. Instead of focusing on true secure environment within browser we still need to worry what extensions are doing. Extension need to have only one right - to do the thing behind reason we install her. I do not want to think if some developer is going to make extension and misuse files and information on my computer or do any other way of abuse or harm. We - users - want first and foremost secure usable browser, good engine behind him and not some trivial things that could come later at any time in some boxed secure environment when talking about extension and graphic skins when talking about interface. About interface... You moved refresh button to left corner in 59? I will notice that you should develop separately Firefox for mobile users - phones and tablets and not impose that kind of browsing with desktop and laptop versions and users. Because this change stinks to me that is taken from mobile versions development. Who on earth keeps mouse pointer constantly on left upper side of monitor when it is just natural to be and to look at middle of screen? Now I must stretch my hand to left upper corner because someone think it is cool or what? What about ergonomic aspects of using monitor and mouse? Just look and read this page-question in any HD or better resolution monitor or TV and tell me where you eyes are? In middle or you are looking for something on top left corner while reading this? You should move all buttons to middle of screen not opposite. I will consider that cosmetics but with all problems that 59 has introduced this is also one thing that should have been carefuller considered after engine change to better not to worst. And tabs have become smaller, it is harder to read headline of page, next thing to expect is to become like in chrome - totally unusable with many opened tabs, you can not find page by name in tabs - just by guessing and/or luck. What is with you people - developers? Aside from engine that runs Firefox most important thing is ergonomics and easy of use. I can imagine that developers made all this changes and that some people said COOL to them - do it - and we got 59 build, but this is not cool this are big problems on all fronts... I was hopping that there would be some fast miracle patch to solve all this after 59.02 but after month has passed I am forced to downgrade 59's to older versions and in future I would consider should I escape from Firefox especially for critical task that requires browser with latest updates and secure environment in order to decrease security risks because I will not update to 59 or any future release if this problems persists. I started Firefox intense use with V2 and V3 decade ago and now I am in position to ask myself what next? I have seen problems like this arising with many good products and many good companies that in one moment of time think in their leadership - management it is cool to change everything, and then using viewing product from developers stance and not customers for development. In such cases companies start loosing customer base and if they are lucky only with hard work and by admitting mistakes they can survive otherwise their future starts to be uncertain. Typical example is Yahoo or when talking about browsers Netscape when AOL management "vision" destroyed it. I wish all the best to Firefox and please understand all this as good reprimand of your beloved user in order to become better and not as some angry user reprimand not considering developers hard work, we all make mistakes we are humans...So we need to improve...