It's not discoverable--the only clue it's there is a tiny arrow. On the old bar it was totally obvious where the links were to jump to other properties.
It presents an inconsistent user interface. If you move the pointer in from the bottom, you're on the left nav. If you move the pointer in from the top, you're on the hover nav. It would be like getting two totally different neighborhoods depending on whether you drove in from the north or south.
It requires precise mouse choreography. It's not enough to aim for the target, you have to follow a specific path to get there (especially true with the extra fly-out submenu). If you don't, you have to go back to the beginning and start over. The old bar was a fixed set of targets--easy to hit from wherever.