Pros: Excellent control, good fit and comfort
Cons: Takes a while to tighten properly
The boot is narrower than my previous pair and this seems to have improved the response. It also required me to get a new set of very thin insoles. I currently have an injured metatarsal resulting in a swollen right foot and the tighter fit caused my toes to go to sleep until I got the thinner foot bed. I used the Sole Softec Response foot bed and it worked better than either a heat molded ski shop foot bed or a podiatrist made orthotic.
The MC3 has optional laces on the inner boot and this really snugged down the boot on my foot so that I could tighten the outer boot. It takes a lot of tightening to get the boot snug and you will have to go over things once more after your first run.
How it skied: Great. Once you get the MC3 tight, you will find it very responsive. I used it while doing Talon crew (race crew) at the 2015 World Cup in Beaver Creek in December. I used it on Fisher 180 cm cheater race skis and on all mountain Dynastar Powertrack 89 in 179cm.
The MC3 is adjustable to three stiffness ratings: 110 120 and 130. I left mine at whatever it came set in from the factory and it seemed fine. It was plenty stiff for work that involved sliding down an icy race course with a 40 pound pack on your back. I'm a fairly fluid skier and found the factory setting excellent for free skiing on piste or through the crud and bumps.
My only experience with them on the powder was on a set of racing skis (AKA bottom feeders) so I can't say how they would work on powder. They should be fine. My normal posture when using race skis in the powder is horizontal and I managed to avoid this so perhaps they are better than just fine.
Overall an excellent high-performance boot for someone who wants something more comfortable than the typical plastic boot. They shouldn't pack out either as you can tighten them more than a typical boot.
The only caution I will make is that your foot has to fit this boot- It is not a squishy soft boot that can fit any foot. This is a high performance boot so it's going to be relatively tight as I found out. If you have an odd foot, try it on carefully in the ski shop to make sure that it works for you.