I've used Cyberfox as my default browser for well over a year because the developer is so accessible and dedicated. I've seen version 1.2.3 of Cf out before Ff 1.2.3 is out and at worst, Cf 1.2.3 will be available withing hours of Ff updates. Having said that, on my X64 W7 SP1 (previously, now W10) I often have various issues for several days after Cf updates, although I'm sure there are issues with Ff updates too. An example would be Cyberfox/Sanboxie issues (I guess you could blame Sandboxie) on certain websites that do not occur with Firefox. I also often test Nightly. Last week, however, I noticed on Major Geeks a new Ff beta and it included a x64 version. I enabled it as my default browser after several hours of use and I'm really impressed. I realize that speed-battle may not be the be all and end all of browser testing but this v 41.0b9 scores the highest every time. It may be indiscernible but a score is a score (e.g. just now: Ff 1483.22, Cf 1416 and Nightly 1423.11). The thing is, that Ff x32, Cf or Nightly might have the highest score when I'd make the comparison. I have yet to see this Firefox beta not have the highest.