Interesting thread. I've read thru some of the posts, and maybe this is just out of habit, I don't do a direct belay when belaying a leader. I've had at least a couple of situations involving a falling leader on a runout climb where I've had to move to take in slack or had to yard in large amounts of slack that I wouldn't have been able to do had I belayed directly off an anchor.
A direct belay makes sense for situations where you're belaying a second who is much heavier or less experienced but most of the I prefer to redirect the rope thru the anchor but still belay off my harness. I just have a hard time getting over the scenario where you're belaying directly off an anchor, which fails, in which case your leader is absolutely screwed.