Awesome, and in my native language I'll say : magnifique ! Rated 5 out of 5 stars

Works fantastically well in my Thunderbird (actually version 14) with >>ALL<< my search engines installed on Firefox ! (it links DIRECTLY to my french Google, image Google, Bing, Yahoo, french Wikipedia, french Amazon, american Amazon, french eBay, Youtube, WordReference, etc.) simply by setting the max number of search engines in the extension... to my 10 prefered engines I have installed in my Firefox.
Thanks also for the ability to link to dictionaries. In this part, I'd like to suggest a link to the very known WordReference (if you don't know it... it's a dictionary online for the 15 most used languages in the world and it also includes the totality of the prestigious Oxford Concise English Dictionary (see http://www.wordreference.com/definition/) and one of the largest thesaurus and one of the biggest synonyms' index and a three language verbs' conjugator ! And all that can by freely assisted, on demand, by linguist helpers (some of them are even professionnals) in internal forums ! I'd like to have this very known WordReference in the list of the direct dictionaries. Possible for a next release ?

This review is for a previous version of the add-on (0.7.4). 

Thanks for the good review! Appreciate that. Next release is almost ready (with fixes for Google and Yandex translations, they changed a format again). I'll try to include WordReference to the next release (that depends on the availability of API or parseability of web page)
Update: Wordreference added, will be available in the next version