In between e10s, Servo, and the new developer theme in the current Nightly, I feel like Firefox is finally starting to become more competitive to other browsers again. I switched to Chrome because it seemed like Firefox was becoming more and more dated in comparison, both in terms of technology and UI. I still have some gripes with Firefox at the moment, but I'm beginning to seriously consider switching back.
This is obviously anecdotal, but both e10s and the Nightly in general have been remarkably stable during the time I've tested them.
I often have hundreds and Chrome just dies when this happens (not to mention it eats tons of RAM -- they need their own MemShrink project). Firefox continues to work and uses far less RAM for the same set of pages.
I had the same experience though I have to admit that some things in Firefox are better these days, like checking where an event comes from, going really deep into objects, referencing other objects, comparing rather big objects.
The only thing I really miss is a view WebSocket frames. In many other cases I ended up preferring Firefox Dev Tools which I think while a bit harder to get into are more powerful.
But that might really relate to what precisely one is doing. I am not a web designer.
The only thing I'm missing in either browser is the ability to ignore jQuery as I'm debugging. Stepping in and out of jQuery (and other libraries like underscore) is a pain.
The Firefox debugger should automatically blackbox minified sources. You can also click on the little eye icon in the debugger panel to manually blackbox sources.
You can also use the developer toolbar to run a command like `dbg blackbox --glob *-min.js` etc. to blackbox a bunch of stuff at once.
I've switched back to Firefox (initially because Chrome kept crashing after 1-2 hours on my machine). Now, I really like it, primarily because I can mess with userChrome.css. But I'm concerned that e10s will reintroduce the instability that caused me to leave Chrome (though I have no real evidence for this).
This is obviously anecdotal, but both e10s and the Nightly in general have been remarkably stable during the time I've tested them.