Programming FireFox Extensions

Here's an interesting link to a tutorial on creating FireFox extensions, Firefox Extension Development Tutorial :: Overview. I'm a bit interested in dabbling with FireFox extensions out a of desire to just hack something, and this has the added benefit of being done with Javascript. I hate the idea of using VBScript for anything since it's a crap language. Javascript is so much like C, Java, C# etc. that it wont be too much of a diversion from the mainstream stuff.