Not that I really have a need to install it, but I'm just curious. The last I knew, Firefox on the mac was pretty much a total joke. I remember for the longest time, anything you tried doing on the mac side of things with Voiceover, it would continuously give the dreadful busy busy busy message.
I hear it kind of sort of got better, where you could kind of ish, key word here, kind of, ish! navigate the menu bar, address bar, etc, but as far as the html web content area, it was still pretty much forget it. I do remember a couple of months ago trying it, and sort of got the preferences settings area to read, but even that was darn near impossible. Focus jumped all over the place randomly, and hardly worked at all. Plus, when trying to toggle some of the settings, it didn't look like the changes took.
I know on iOS it's doable, but again, I'm very specifically here speaking of doing this on the mac, not on iOS.