Here's my standpoint. I've been using the preview of Quantum (ie Firefox nightly) for a few months, in parallel with Chrome and Canary. (caveat: I'm not doing any front-end dev, so the grid-inspect which is supposedly awesome don't really get my excited ;-)
So far I like it a lot. I have too many years of habits in Chrome to make the switch completely, but I do use both at the same time on a daily basis.
Here are a few features I do love in the new Firefox:
- Container tabs! Because I'm paranoid, I have several google accounts to have several Chrome profiles, so that I get segregated context for personal stuff, work stuff, production stuff, and personal but serious stuff (banks, ...) Firefox introduced "containers" which are separated context so that no cookie, history, localstorage or anything personal is shared between these containers, but you can manage this under s a single firefox account, with a single set of extensions, bookmarks, ...
- Tracking protection enabled by default, everywhere. (I do use uBlock, privacy badger, and uMatrix on Chrome, but having this built-in the browser feels good)
- native "reader" mode to remove the shiny stuff. No need to add an extension (I'm still amazed Chrome don't have this natively)
- send the tab to another device. Awesome to share stuff between home and work or mobile!
- embedded Pocket (I read a lot on the go, especially in the subway where data is not available everywhere, so I'm a big Pocket user). No need to add an extension
- native webpage screenshots, no need to add an extension
I would not say it's a game changer and people should switch.
But I would still recommend to people to give it a try. It's a really modern and fast browser, and I wouldn't be surprised to more people adopting it. Especially with all the privacy concerns that keep increasing. Using Firefox+Duckduckgo as a default search engine (duck duck go has improved a lot imho over the last years), gives you a good and easy starting point.