I am not a travel newbie, but I believe it's the first time I heard about Hipmunk. What was so innovative about them? It looks like yet another travel aggregator among at least half dozen of it's kind: Kiwi, SkyScanner, Kayak, Expedia, Priceline, Orbitz...
The big thing at the beginning was the ability to sort by “agony”, i.e. a combination of travel time, number and length of layovers, and carrier quality.
To this day I still find it the best search interface if price is not your only concern. It’s compact and easy to tweak.
Unfortunately, the way they handled payments was too US-centric, which meant I often ended up looking up a flight with them and then actually booking it somewhere else (because you don’t want to book an Euro trip with some unknown US operator who may or may not be accountable if anything goes wrong). Also some of the cheapest airlines were typically not included.
