I guess the theory is that bass is non-directional, so if the crossover sends suitably low frequencies to the side-mounted speakers it doesn't matter that they're not aimed right at you. And it gives you the ability to have a bigger woofer in a narrower cabinet. And I get their "earthquake zone" comments (if the woofers are pointed into the corners).
The reason I ask is that I have a friend who is considering something like this, hoping it means he doesn't have to buy a separate subwoofer. His setup is in a "wide" living room, with the TV way off to one side of the room. The woofer in the left speaker is going to be firing right into the corner, while the one in the right speaker aims at... well, nothing. It screams "unbalanced" to me, but then... non-directional... so maybe it's OK... I just don't know. What I do know is that when I finally got a sub myself I couldn't believe how much of a difference it made. I kicked myself for waiting so long. So if anyone ever asks me if they should get a sub I always say "Hell, yes!"
So, any thoughts on how these things might work?