I took a trip to Boston and New York last year, and I booked it through Orbitz.
I was snowed-in at Rochester and one of my flights was canceled so I couldn't make my connection...no problem. Orbitz fixed the whole thing for me and re-booked me on flights for several days later (when the weather cleared) at no extra expense.
It's legit, just make sure you book your itinerary with plenty of time between flights just in case something happens.