Rated 4 out of 5 stars

Would be perfect except for one thing: It doesn't respect my preference to switch to the new tab I just opened. So, I middle click the search engine, but I can't immediately see the results. I then have to click the tab that just opened. I would prefer that tab to be opened automatically (according to my Firefox preference). (Note to Ben Basson, the contact link on your page appears to be broken.)

This review is for a previous version of the add-on (0.4.4). 

Middle click?

Dan, left clicking the search engine should respect your tab preferences. Middle clicking inverts that preference.