I do wonder though, is this performance improvement Windows specific? It's hard to believe that Mozilla could make up the difference in only three or four months.
Edit: looks like Chromium still beats Firefox on Linux: https://treeherder.mozilla.org/perfherder/graphs?highlightAl...
In fact, all benchmarks browsers seem between a quarter and a third slower on Linux in speedometer. That's strange, I wonder if this has to do with the limited availability of hardware acceleration?
Looks like it really depends on the benchmark. In some Firefox gets slaughtered, in some Firefox is the clear winner.