Seopped working Rated 2 out of 5 stars
It worked very well, but stopped with Firefox 29 and still the same with version 30. When the Wikipedia or Wiktionary window should open only a small window shows a message "Looking up xxxxxxx on Wikipedia". I removed and reinstalled, but no way.
The developer does not offer any contact, but only a way to donate... strange. Not possible to give this add-on a 5 star, as it might deserve, because this seems to be permanent.