I got this last year. I've hiked in the rocky mountains with it. I will say that if it's hot out, the wearer will get wicked hot and sweaty. The kid, not so much. I can only put this on by myself if I can find an elevated surface where I can sit down and strap the kid to my back. The last time I used it in November I found a couple of stairs, put the kid on the top stair, sat on the stair below it, and presto- easy peasy. My son is 15 mos old and over 30 lbs. I did a relatively easy 5 mile hike without any discomfort. The only beefs I have with it are that adjusting the torso height can be a PITA. I'm 5'6 so I had to raise the waist band up to fit comfortably and it doesn't sit right when you adjust the velcro too high. Also, both zippers that keep the hood contained broke off- not a big deal because it doesn't affect functionality, but it was surprising to give it a pull and end up with the zipper in your hand. I'd buy it again and I can forsee us continuing to use this comfortably until our son is up to the 40 lb mark.
ETA: we also have an Ergo. For back carrying while hiking this wins because it makes it easier for you to keep your balance on uneven surfaces and lifts the kid off of your back so you both don't get yucky sweaty. For running errands or suburban mom type things I prefer the ergo since it's easier to get on, not as ugly, and easier to transport.