Their flights are worth it, even if you need to make a connection and check baggage, if it is a location you are going to anyway on one of the airline's discounted fares. So a normally $500 round trip fare goes down to about $300 with the airline's sale, and with SQM's 50% discount, it goes down to $150, round trip.
That's like a $150 fee to go somewhere you're traveling to anyway. No frequent flyer miles, no, but if you don't fly too often, or aren't accumulating points on the airline's credit card (or some other system), it won't matter. You can always use whatever frequent flyer/buyer credit card to pay for the flight through SQM and earn points that way.
Also, their bus shops refund the full fare, so they're a great deal, too, especially if the trip is to a popular location where it's hard to find a reasonable bus fare. Again, like a $15 (SQM minimum refund) to $50 (SQM maximum refund) fee each direction ($30 to $100 total for round trip) to go somewhere you were planning to go anyway.