Broken and Discontinued Rated 1 out of 5 stars
I can only assume from the lack of communication and updates, that the developer has ceased work in this add-on.
This add-on definitely provides a very useful functionality. However, not only it is already a bit buggy when installed with certain other add-ons, in the upcoming Firefox 25 it will break completely.
I have written my own add-on, called "FindBar Tweak", that provides a similar "Find in All Tabs" feature, which is both very powerful and easy to use at the same time. Unless work is resumed here, I would invite everyone to switch to FBT, ensuring it will remain compatible with future versions of Firefox!
I'm sorry for the spam, but I believe my add-on now becomes a necessary alternative to Find in Tabs, which will stop working completely in the very near future.