Just FYI, it's good for finding routes/times and indicative pricing, but sometimes going to the airline's website can yield savings of hundreds of £s (I've personally encountered this >10 times this year on non-LCC long haul routes).
Yeah SkyScanner is easily the best for international flights. Obviously in most countries a locally based competitor is going to be better for domestic flights.
I tend to use Hipmunk for both domestic and international flights; I haven't seen anything that comes close to Hipmunk's UI for presenting flights. What's the main advantage of Skyscanner?
My impression is coverage, skyscanner appears to have pricing from a huge number of sites/resellers which is important because in my experience the same flights from different sites can have significant discounts over each other.
I've tried using other sites before and while the UI on hipmunk is nice my experience was that skyscanner normally found options which were cheaper or didn't show up at all.
But I live in the UK and typically I'm booking long haul to Asia, I don't know if the situation is different elsewhere in the world or if perhaps skyscanner is concentrating on the UK market as its home market to an extent.