The scrolling just does not feel like other native apps on Windows or Mac. It's slower. Most other apps, including Chrome, feel the same as other native apps when scrolling.
The odd font rendering is another problem. Fonts in Firefox look different than fonts in other native apps.
The friction is far too high. It's impossible to scroll more than one screen or so in a single swipe. It's maddening. I can't fathom why they didn't just use the OS default behavior.
FWIW, the release notes for Firefox for Android call out scrolling performance improvements in 3 of the last 4 releases. Might be worth taking another look :)
I have both Firefox and Chrome installed. I can't tell the difference between the two in terms of scrolling. On both I can flick and it keeps going for ages. It sounds like a bug to me.
It could have also been fixed. Last I tried was around a year ago.