I've owned about a dozen Merrell shoes of various configurations, mostly Merrell's "moc" designs. I purchased "Moab Waterproof" shoes from Amazon and am very happy with them. Sizing is true -- the 7.5 (US) fits me great like all other Merrell 7.5 shoes.  I can't comment on durability as I haven't had them long enough, but all my other Merrells have held up great. I notice some potential confusion among the reviews of the Moab Waterproof (unless Amazon is grouping reviews of slightly different products).  Some reviewers mention Gore-Tex; that is a different shoe.  Merrell's website details two models -- the Moab Waterproof and the Moab Gore-Tex.  You can also tell because the Gore-Tex model has a badge on the shoe that says...wait for it..."Gore-Tex", while the Waterproof is badged "Waterproof".  The Gore-Tex model also carries a higher price tag (no surprise).  I haven't had these in the wet yet, but I have considerable experience with both Gore-Tex and similar, non-Gore-Tex membraned motorcycle gear (I ride throughout the year in the northeast US).  Gore-Tex is the King,  but most of the other membranes work just as well as far as waterproofing.  I find the difference is that GT does a slightly better job at venting. Just make sure when you order you are getting what you want: Gore-Tex or whatever Merrell's proprietary membrane is.

Addendum August 2013: I've done a couple of long hikes with these and they've been great.  My feet have stayed dry during rain and shallow creek crossings.  Keep in mind these are not boots, so if the water level rises above the shoe opening, all the waterproofing in the world isn't going to stop your feet getting wet.