They actually did, the recent switch to multiprocessing made a massive difference. I've been happily using Vivaldi for a few months now, but I'm tempted to go back to FF as the speed gap has been wiped out of late - only cold startups are a bit slower, actual pageload is absolutely on par or better. This on Mac, at least, but I expect it will have been similar on other platforms.
Last time I tried it still was slow... I'll give it another try.
When was the last time you tried? R55 is way snappier than Chrome. Nightly is also fast.
Yeah, a lot has happened in the past few months. And there's still more things scheduled for the next few versions...