Likewise, on DDG, !w <term> searches wikipedia for something, while !hn <term> searches hnsearch for something. And I never had to configure anything. The best part about DDG is what someone mentioned earlier in the thread, the fact that so many sites are already in the list. If I've never searched Stack Overflow before, I can !so just based on a guess, and most of the time it is right.
Those are just two examples that I gave. Two examples of customization that aren't available that I have are 'wf' set to search Wikipedia for <search term>+ " (film)" and 'wtv' set to search Wikipedia for <search term>+ " (TV series)".
