In general, the Photon interface changes every detail on the UI, both the toolbar icon and the transitions and page loading effects. Some new features also include a Firefox library (menu for quick access to browsing history, bookmarks, saved on Pocket and synced tabs), Screenshots (screenshot).
New menu to access multiple tasks
New Tab page is also completely new, using more reasonable space, displaying recent searches and sharing articles on Pocket. Pocket buttons also remove from the toolbar and switch to the address-search bar.
Mozille advertises that Firefox QUantum is twice as fast as Firefox 49, and uses less memory than Google Chrome 30%. According to Speedometer 2.0, Firefox 57 is twice as fast as Firefox 52. Partly because the new CSS engine is Stylo with architecture that handles many processes, prioritizing smarter tabs . 'We push ourselves to keep up, and sometimes even ahead of Chrome,' said Mark Mayo, vice president of Firefox said. 'We doubled the speed of Firefox this year and the goal is to duplicate it again in 2018'.
For many people, the biggest change of Firefox 57 is not the interface or the things that are not visible in the engine, but the fact that they don't use many old add-ons anymore. Developers have been warned and have time to prepare for this.
See also: What extensions are no longer working on FireFox 'fire fox'?
Many add-ons are ready to use WebExtensions. Here is a list of usable extensions in Firefox 57. https://addons.mozilla.org/en-US/firefox/search/?tag=firefox57
Firefox 57 is an important milestone not only for the Firefox project, but also for Mozilla and other open source software in general. No advertising about Quantum is too much, it's really faster, stronger, better than before.
Whether this will bring you back to Firefox, the competition between large browsers will become more attractive. Google will obviously be unhappy and will also make improvements to its browser.
Firefox is not just a browser, it also represents the open source community
Firefox plays an important role to get a 'free technology zone', not controlled by big guys like Apple or Google. Their mission is to keep the web open and competitive.
If you use Windows, Mac, Linux, you can download Firefox 57 directly from the homepage.https://www.mozilla.org/en-US/firefox/ If using Ubuntu, Firefox 57 will be updated automatically with supported kernels (Ubuntu 14.04 LTS, 16.05 LTS and the latest Ubuntu version 17.10). Versions for iOS and Android will also be released soon.