Just booked a SFO<->YVR itinerary with them travelling in March. Credit card shows charges from United and justfly.com ($12.95). Adding them together matched the correct total justfly.com when I booked.

Got 2 separate United reference #s (hacker fare) which is fine. Checked both of them on united.com, and got ticket #s, full receipt, and showed same selected seats when I booked on justfly.com

Looking at both receipts, it showed the base fare and taxes etc, ticket #s, for each leg, and looked normal.

Why did I book with them? They were more than $200 cheaper than united.com on a $4xx fare. I found them through kayak.com. Kayak showed this hacker fare, saying it could be booked at united.com. However, united.com showed the $4xx fare when I went there.

Tried all other sites suggested by kayak.com, and justfly.com was the only one who could book this fare.

Wish me luck. So far, I don't think I will have trouble.