Janky scrolling on arstechnica.com e.g. http://arstechnica.com/apple/2015/04/like-all-mobile-wallets-before-it-apple-pay-struggles-with-retailers/?comments=1 Smooth scrolling in Opera / AOSP browser.
I reproduced this with Fx44b4 Win10. It may be related to the GC, I saw some big block in DevTools - Profiler, although it seems to be very short.
Works fine on version 49. Not as smooth (lower framerate) as stock but acceptable.