Watching them on that hill at the end, it looked pretty steep, although as the commentators said, it was worse at the bottom. I suspect I'd be puffing going up that at any speed.
It looked a bit like Cancellara was watching for the two on his tail, and getting ready to try and out-sprint them. Since what he wanted was just time, it looked to me like he should have ignored them and just hammered on as fast as he could. If he'd got a small gap in before the peloton, he'd have gained a few seconds instead of just staying in the same position.
It's going to be interesting to see how Sagan does.