Since Firefox 23 the keyword.URL preference lost its purpose. However with it an interesting feature of the awesomebar got lost as well, because it is now impossible to use a different search engine for it and the search box.
If your profile is missing keyword.URL
(note the uppercase!) you might want to use this value
. Otherwise every other string that used to work should also still work.
The approach in which this addon brings back the old behavior is indeed a very ugly hack (see also the name), so it can occasionally happen that other features related to search break. At this point this addon is supposed the be strongly considered experimental