Say what you want about Google/Alphabet as a whole, but Google Flights is incredible. It's absolutely amazing how quickly and largely that Google crushed all its competitors in terms of usability. Kayak, Hipmunk, Orbitz, Skyscanner were all my go-to's at one point but G.Flights is far superior in so many ways. It actually remembers your airline preference between searches. You don't have to beg or change settings to…
I agree that its real-time inventory and pricing availability has been a total game changer in the UX department. Presumably their acquisition of ITA gave them the ability to respond to queries in real-time which enabled all of the (quite excellent) features you pointed out above. There's just one problem -- because a ton of the data is cached, or precomputed, or however it's done, a substantial and frustrating amoun…
My solution so far is to search for broad prices for my approximate dates on Google, and when I see something promising open a new tab and go straight to the airline's site where I search for an actual offer for a specific flight.
I've found Google Flights super useful this way, though I guess they make less money on me than they could.