Hey, this is kind of a pet peeve of mine, but
it's Firefox, not FireFox. When you put CamelCase on it, it sounds like one of those "freeware" products that people only release for Windows and make you think they're spyware because they don't release the source, even though they aren't making a profit.
And, I recommend just presenting it as a Greasemonkey script, and maybe linking to the Greasemonkey website – I don't think people should have to install and use a whole new browser just for one script that acts upon one site. I think Firefox is a great browser (definitely the best one available on Windows, and one of the best on Linux, although I use Konqueror too), but the argument for that should be placed elsewhere.