If you're like me and can't live without single key shortcuts, you're probably a legacy Opera user, and Firefox probably isn't your main browser today. I'd use Firefox more with a single-key shortcut feature.

There don't appear to be many single-key shortcut extensions for Firefox. I only found one other, which only provides tab navigation; this one provides forward/backward. I live and die on both of those options, so this one wins on features. But the lack of competition is also part of why this one is four stars, not three.

The default shortcuts are z/x for back/forward, which are legacy Opera. For previous/next tab, it's c/v. At least since I started using Opera with version 9.2, it's been 1/2 for those shortcuts, so c/v is not muscle memory (though it is right next to z/x). That said, this extension does provide a UI for changing the shortcut keys - but when you try that, it actually unbinds all of them. You have to remove and re-add the extension to get them back. Thus, stick with the z/x/c/v defaults.

The shortcuts also don't always work on the first try; z/x in particular often require two presses, and they don't work on New Tab or Firefox Settings pages.

That is enough downsides that it would ordinarily dock two stars. But considering the lack of better alternatives, 4 stars it is. After all, even not being as smooth as Opera 12, it's probably still going to increase how often I use Firefox.