Pros: Warm, snug, fixes many fit problems
Cons: better to have a pro work on the fit
I was in the middle of a miserable boot fit season when I bought these. I am a part-time ski instructor and had lugged through lessons where I had to remove my boots at lunch to let the hot spots heal up what they could before the afternoon shift, and was desperate for a solution. I settled on these with the help of a bootfitter, and they were an immediate and dramatic improvement. I have very, very narrow heels (12A business shoes) and can feel how well this liner has filled in around my achilles. It works great with my custom footbeds - still allowing the articulation of the foot I want and great feel over variable terrain off-piste (where I do most of my "fun" skiing).
Compared to the stock liners, there is no comparison. I find these liners pretty easy to work with - although you do have to pay attention to the way the wrap falls over the bridge of the foot, they open up easily for when you put on or take off the boot. They are warm on cold, wet days and I feel the support I want on the steeps I prefer to ski.
I felt a lot more comfortable getting them "cooked" at my dealer - who knew exactly what he was doing and guided the quick process. I have also added some more pads to the outside of the ankles where additional tension was needed, but I don't consider this a big deal considering all the other problems these liners have improved. I don't even buckle my boots for a lot of childrens' lessons I teach since I got these liners - no heel pumping, no problems up to blue terrain. Great fit, comfy, and additives to prevent odor issues - well worth it to me.