Computer A:
Sometimes I cannot close tabs by clicking the X, or refresh/go-forward/go-back using the buttons next to the address bar.
Computer B:
Sometimes I get downloads that have "Unknown time left" (0 bytes/sec) when the X of X KB/MB is 100% and you can't remove it from the downloads dropdown.
I just discovered a new bug on Computer B, clicking the hamburger menu doesn't do anything.
Both are Ubuntu.
(I'm not a fan of the new menu in Firefox Beta for Android. I guess it looks nicer due to the greater whitespace, it just break muscle memory and has less options/selections.)