Switched from Chrome for privacy reasons a couple of months ago. As a webdev (and hence heavy DevTools user), it feels excellent, the inspector's a little bit faster, and having containers for Facebook and Google tracking services is excellent. Spell check in text boxes doesn't work though - apparently it should, I have no idea why it doesn't.
Yeah, I've made some big reports already (CSP errors from undefined source when using Stripe with LastPass enabled) but I want to check it out more before bothering anyone - maybe it's my Windows language config
For spell check, I've noticed I have to right-click and check spelling. I actually kind of like not having the browser second guess me, but not sure if this is an intentional default on FF's part.