You might want to try Firefox's built-in Web Console. I switched a year or two ago when it was less powerful than Firebug, but notably more stable, and I haven't gone back since.
> except for an annoying OS-X multi-screen bug where it screws up the sizing
Can't argue with you there. At last exiting full-screen video no longer takes the entire browser out of full-screen.
You might want to try Firefox's built-in Web Console. I switched a year or two ago when it was less powerful than Firebug, but notably more stable, and I haven't gone back since.
> except for an annoying OS-X multi-screen bug where it screws up the sizing
Can't argue with you there. At last exiting full-screen video no longer takes the entire browser out of full-screen.