Not kidding about the zippers
These could be the perfect MTB bootie. The sole is awesome and seems super rugged. Great grip in the snow from the rubber toe area and the rear seemed to provide enough of an opening for the treads from my shoes to poke through w/o issue.
They seemed to do a pretty good job at insulation. Probably still not enough to keep my toes alive with my summer shoes and a pair of SmartWool PhD socks underneath w/o chemical warmers once it got much below 20F, but I think I'm going to have to break down and get a set of dedicated winter shoes to accomplish that.
They were true to size, were very easy to get on and off, and stayed put once on. They don't seem to get in the way of cleat engagement w/ SPDs. No snow or mud intrusion and kept my feet dry through large amounts of snow and mud and a couple of creek crossings.
Unfortunately the zipper pulled past the stop as I was putting them on for my second ride in them and my LBS was talking 2-3 weeks for a replacement pair so I wound up exchanging them for a pair of PI Barrier MTB booties. I don't think I like them quite as much as the Enduras (short of the crappy zipper stops).
I'd probably go w/ a set of these over the Pearl Izumi ones if you can be really careful when you're zipping them up.