I have been a long time Firefox/Waterfox user but after getting tired of lackluster performance from Firefox over the past few months I was seriously considering a switch to chrome or something else until I found out about... Firefox Quantum!
This is not a comprehensive review as I'm not a browser expert, but I know what I like and I like Firefox Quantum!
Pros:
-Simple installation (beta in my case) keeping all your old bookmarks, saved logins etc...
-Super fast, I have not measured it in any way but it is perceptibly faster for sure.
-Subtle changes to the layout, better customization of UI.
-The few add-on's that I have installed (that are Firefox 57+ updated) are working really well.
Cons:
-I only just found out about it.
If you really like the snappy speed of Chrome, but generally prefer Firefox it is definitely worth a try!