Rated 5 out of 5 stars

Hi Wladimir, this looks like a great start!

Looking through the output in the Error Console .. looks like one has to sift through a mountain of data in search for a few gems. I guess you can say it's more of a "presentation" UI thing, but this looks good. Difficult to use on a daily basis simply because I can't afford to dig that much.

A way to drill down would be helpful. For instance, if I just want to see all the output from eval() and document.write() and ignore the rest.

This review is for a previous version of the add-on (1.0). 

Trying

I already changed the view from Error Console to a dedicated window with search capabilities, this will probably be released today. Also, there are now two views, one for things being compiled and another for scripts that get executed. The latter should reduce the amount of code you have to look through considerably - unfortunately, right now it tends to be incomplete (https://bugzilla.mozilla.org/show_bug.cgi?id=475334).

As to eval vs. document.write - that would be https://bugzilla.mozilla.org/show_bug.cgi?id=449464