I've used this add-on without issue in Palemoon 25.x and Firefox 32+ (haven't upgrade to 34, yet) for quite some time. I tried all, but maybe 1 or 2, of the other site searches and this one had more of the options I wanted, than any other, including the unobtrusive design. This thing is pretty sweet and a must-try.
I absolutely love the ability to change domain and sub-domain on-the-fly.... the only thing this add-on is really missing, is the ability to alter the search, also, "on-the-fly" to be enclosed in quotes or not (as is, you have to go to options to change that). Other than that, the only other "minor" request that I'd make is for the middle-click to load a new tab in the background, as opposed to foreground, but that's very minor.