Buy a touring boot and you generally sacrifice downhill performance; flex ratings seem to apply differently in this category, or else they're simply exaggerated. Not so with the MTN Lab. Our very first experience of this boot was in the freeride area of Pic du Midi, in fairly fresh but chopped up, wind-blown, and freeze/thawed snow. The 120 flex was never in any doubt and powered through powder and crud on every turn. And on the pistes lower down there wasn't even a hint that this was anything other than a solid, stiff, advanced skier's boot.
But with all things 'all-mountain' there must be a compromise. And the MTN Lab's compromise is on the uphill. Marketed as a free-touring boot, it does have credentials; under 1.6kg, tech inserts for pin binding compatibility and an easy-to-use walk mode. But the range of motion is limited compared with other similar boots, and of course much lighter boots are available (Salomon's MTN Explore boot for example is more than 200 grams lighter, but sacrifices way more in stiffness than its 110 flex rating would suggest).
Another minor gripe is that this reviewer has long been a fan of the close performance fit of Salomon's freeride offering, and despite similarities (98mm last, tight heel hold) the forefoot shape seems at once narrow at the sides and vertically voluminous - it's worth sizing up in comparison to other Salomon boots.
All that said, if you want to tour in order to reach great skiing, then Salomon have put the compromise in all the right places; ie, the uphill. Rather than view this boot as a tourer that can handle the descent, we'd categorise it as a genuine everyday boot, with better-than-average climbing ability. It's all about the down.