Xbox 360 Fall Dashboard Update appears to have completely broken my Xboxes

At the risk of sounding dramatic, is the  2007 Xbox 360 Fall Dashboard Update a complete  nightmare for anyone else, or is it just me? I've installed it now on three Xbox 360s, and the results are the same: All three now perform horribly, with frequent pauses in games and in the blade UI. On the Xbox 360 in the living room, which we use as a TV interface via Media Center Extender, it's even more exasperating: You click on something and then just have to wait, often for up to a minute. This is particularly bad when you want to do something like rewind TV just a few seconds because you missed something. It just freezes up. Surely I'm not alone on this one. Is anyone else having these issues? Why haven't I seen anything about this??