I don't have the "new" Manta but I've used the previous generation for the past few years on several overnight and day trips on Hood, Rainier, Adams etc... and several classes with the Mazamas during the spring. They are stiff enough for some front pointing and general glacier travel but are also comfortable for walking. They are very water resistant if you wax them properly. They accept step in crampons. The sole is sticky enough to scramble on wet rock but I wouldn't want to do anything too technical in them. They are warm in 20 degrees if you're wearing mountaineering weight socks. I really don't have any complaints except perhaps for weight, although they are still lighter than most plastics. If I had to buy another summer mtn boot, I would probably go with with Scarpa's Charmoz or La Sportiva's Trango GTX because they are each a pound lighter. In the end it's all about the fit - I have a low arch and wide feet and after the boots broke in I rarely got a blister. Bring your preferred sock combo and try on as many pairs of boots as possible.