Rated 5 out of 5 stars

>Firefox can't find the file at chrome://jetpack/content/jetpack.xul#develop.

Ubuntu's firefox-3.5 binary file name is 'Firefox-3.5'. This occurs the error.
To avoid it in a hurry.
xulapp.js 57
if (Application.name == "Firefox") {
-->
if (Application.name.match(/^[Ff]irefox.*/)) {

This review is for a previous version of the add-on (0.6.1).