The late merging I'm talking about is when the left lane is packed with cars, and someone decides to gun it and use the last 30 feet to merge into traffic. They also switch into the merging lane from the left lane to pass people, only to find out they saved 15 seconds because they're moving back into a traffic jam.
Zipper merging works when there's a clear line of sight and the road is straight. When its ontop of a hill though, shit feels way too close for comfort.