You get used to it - UI is slightly different in some areas, but it lacks for no major features and performance is good, like firefox in general.
I've found it's extremely valuable to be developing sites in Firefox using the dev tools simply to help catch issues that the rest of the team ignores as they're all stuck on Chrome. Fights monocultures by default!
I remember Firefox being seriously lacking in some WebSocket dev tools that I needed. But I checked again and they're there. So it seems like they are actively improving the dev tools.
