I just picked up a Mud River and am impressed with it. No worries about it being water resistant. What I really like about it is the oversize option they offer for large kennels. It allows enough space for me to slide a piece of foam insulation above and below the kennel. I typically drive three hours or so in cold temps to get to my late-season pheasant hunting spot, and like to know that my dogs are comfortable in the back of my truck, particularly on the way home after the hunt, when they climb into the box cold and wet. The 1/2 inch styrofoam makes quite a difference, particularly beneath the kennel.
Other than that, the construction is much heavier than the other covers I've used, so it appears that I'll get more years of use out of the Mud River cover.