The Hype surrounding a custom insole.it's a big fuss, but for nearly everyone it makes a difference. the real differences are that you have a warmer foot, a snugger fit, better foot control, and a better boot fit.
your foot is warmer because your foot is supported completely underneath so that your muscles don't have to contract to hold your foot up. relaxed muscles allow for the best blood flow through the foot, hence better circulation, hence more warmth.
the snugger fit comes from the fact that your foot does not have room to move, it's held in place, but in a comfortable way, because the insole is customized to the foot. saying it's snugger is a little bit of a lie, because many people actually feel like there is more room lengthwise inside their boot with a custom insole. this happens because your foot is held back in the heel pocket by the arch support that is built into the custom insole. but, it feels great in a sung, controlled fit kind of way.
better foot control. you fuss for weeks about which boot fits your foot shape best. and you get the boot punched and dremeled. you've got a super fit. everywhere except underneath your foot, where you've got a pretty much flat insole. so, to complete that custom fit you've got everywhere else, you have to somehow or other make the bottom of the boot conform to your foot. once you have done this, you have more control because the boot moves even more instantaneously to movements of your foot, weight shifts, etc. a custom insole helps to align your bone structure correctly, so that your knee is centered over your, and so on. this makes starting from a neutral position much easier, which in turn makes skiing easier.
better boot fit: alot of people complain that their ankle bones don't fit in their boot right, or that they have alot of pressure on the side/over the top of the arch. these are usually not problems of the foot, but rather problems related to misalignment of the foot in the boot. when the foot is correctly aligned in the boot with a custom insole, these problems tend either completely disappear or require very little additional attention. and like stated above, when your boot fits right, you ski better.
so, all that said, i know plenty of hard skiers who don't use insoles. what they do is squeeze their feet into boots that are not optimized fitwise at all and remove the insole all together. this works for them. some people's feet are so voluminuous that there is no room for an insole.
so, maybe it's all bunk. but i know there was just a post from someone about what an amazing difference a custom insole and some shims made in his skiing experience. we do a 100% guarantee on our insoles at our store. we buy back one or two a season. that's not bad.
from my "hyped" opinion, anyone who does not at least try one (you should get a 100% guarantee and a good shop will fix an insole if it's not right) is missing out.
if you're convinced it makes no difference, ski with and without it back to back runs. if you're still not sure, get your money back. just remember that you've got a custom fit in your boot, everywhere but under your foot without a custom insole.