correction Rated 4 out of 5 stars

I don't know what went wrong here. This is my corrected review. After stumbling upon those bugs on first usage, I went again to the add-on's preferences and restored the default engines and pressed OK first to get sure it's in default state. Then re-opened it and did not try to delete all default engines as my first step. This time I first added my own engines. When I finished, I was able to safely delete the default engines then. However, no matter how often I try to replace the menu's label "Define {word}" with "Lookup {word}", that doesn't work. It would be nice if this could be fixed, because looking up a word in a dictionary is not looking up a definition. Also there are people who don't want English in the context menu, adjusting it to their localization of Firefox.

This review is for a previous version of the add-on (0.9.2).  This user has 2 previous reviews of this add-on.

Fixed in 0.9.3

The bug you mention has been fixed in 0.9.3, which also adds ff 3.6 support. It was uploaded about a week ago and will probably soon come through the review process...