This extension was, originally, part of Firefox. I kind of understand the reasoning behind removing it and making it into an independent add-on (faster updating, independent development etc.), but I fear some day Firefox will drop it altogether, like it did with other technologies (let's not talk about WebSQL and the amazing beast that was XUL).

Anyway, this is an essential extension, full of features (don't forget to check its options for more essential features that come disabled by default, for whatever reason) and very light. There are lots of reasons for not leaving Firefox for other browsers, and this is surely one of them!