Very very nice. I would like it better if it used the native python environment already floating around in the system instead but that would probably make compatibility a nightmare. Still, kudos to the ones who wrote this.
Unfortunately it didn't work:
Alex Badea has actually made a pyxpcom extension for Firefox3, but it is a somewhat different approach as it relies on a matching python being installed on the system and other extensions using pyxpcom may not get registered :(
http://vamposdecampos.googlepages.com/pyxpcom