Powertools aka "the userscript" is awesome but all it does is let you go from a specific flight result in an ITA search and click through directly to a booking page sort of like the "Book with ..." link in a Google Flights search result.
It's handy especially for booking itineraries that are difficult to replicate elsewhere, and definitely a useful tool for mileage runners/fare hackers, but by itself it does not help with searches.
FT thread (see wiki for basic info and installation instructions):
http://www.flyertalk.com/forum/trave...-lh-lx-tk.html