Incredible Mitts
I used these mitts on my first climb of Mt Hood in May which was my first venture into mountaineering. I suffer from Raynauld's syndrome and have a tough time keeping my hands warm. I honestly don't think I personally would have made it with lesser mitts. The two layer design is great as it gives options to remove the inner layer when you are too toasty or use glove liners instead. One feature that I LOVE is the pull cords to tighten and loosen. There is no fiddling around trying tighten and loosen the same string on many gloves. It has one string to pull to tighten and a different one to loosen. The dummy strap is very handy as well. I would have lost them in the heavy winds without them during a belay. For most people, these gloves might be considered overkill in many situations but for me they were a life saver. Highly recommend if you tend to have cold hands or going into pretty extreme environments. But again, the two layer system gives them the versatility in various conditions. Highly recommend.

The best for the worst weather
Without a doubt these are my go to gloves in cold weather. I've used them for some of the nastiest weather and they perform better than anything else out there! As for fit, please make sure you measure your hand and see if you hand measurements fall in the middle of size ranges because you want these mitts to be a loose so that you can easily wear a glove linear underneath these OR mitts. Also it makes it so much easier getting your glove on and off quickly in the cold weather. My hand measured 8.4 which is a Medium size mitt, but it was way too tight and the LARGE is the size that I actually needed! Trust me, you will want to get a size larger than normal if the measurements of your hand fall on the bigger end of the size range. With that all being said, these are the warmest gloves to have at a fair price!

First and last Mitts
I bought the mitts for my aconcagua climb in 2012. I like how the lining of the gloves fit well and you still can layer underneath. Im a very small asian guy, mainly 1.65metres with little hands and i bought the small. Fits perfectly. It comes in red and black and the black matches my montane anti-freeze jacket. The only thing that i dislike about it would be the material looks like it can be torn after repeated use, so ill have to take care of it during my climbs. Haven't tried it in cold weather yet, but will be looking forward to a NZ climb this december and putting it to the test.

Very warm
The outdoor research mitt is exceptionally warm. They will be with me on my Denali climb this June. My only complaint is when I make a fist, the outer glove does not move entirely with hand. Overall, a good purchase.

Outdoor Research Alti Mittens - Best out there
Bought these mittens to take skiing in Aspen. They were so warm I was able to wear just the removable liner mitten on some days. They are pretty large (due to all the PrimaLoft insulation) but the drawstring makes them easy to fit snug. The only downside is the slight loss of grip (but expect that of any mitten, as opposed to a glove). I will be wearing them during the Chicago winter - quality product!