A vote for the Yakima Sidewinder. We've been pleased with ours. It differs from the Atoc/Thule in that the pivoting arm is designed to cantilever further out over the side of the car, making it a bit easier to load IMO. (Yes, I've tried an Atoc.) The only complaint I really have is that, due to the cantilevered arm design, the tandem sits a bit further back on the roof than it would with an Atoc, but it hasn't caused a problem.

We still use the Yakima occasionally on our Subaru, but the Honda Odyssey minivan handles most of the hauling of our tandem and triplet since we can fit it inside.