"Pretty flexible for a plastic boot but it's still a plastic boot."
My Koflach (cough*Black Diamond*cough) Degres have been a good plastic boot for me. They're more flexible then the Invernos and Arctis Extreme and climb rock OK, for clunky plastic hunks of bigness, but it's all relative. Let's face it.,, plastic should only be used when you're exclusively on snow and out for multiple days. You put the liners in your sleeping bag, and in the morning your boots are not frozen. For ANYTHING else, like mixed rock/ice/snow, hiking, a long approach, or any day trip, choose a modern insulated leather mountaineering boot. They're just as warm if sized correctly, and leather just climbs, hikes, and feels so much better than plastic. It's night and day.
Did my research and fell in love with these boots. They're comfortable to hike in, I recently did a 28 mile 2-day traverse, w/ +7000'. They lace up easy on the hands. Provide great support for vertical ice climbing. They work with Radone Ski Bindings and my snowboard bindings, so they're great for backcountry ski use, no need to carry two sets of boots. Crampon compatible but with BD you need to order the large toe-bails to fit the boot. Listen to every other internet review and order a full 1 size up, I originally ordered a half size up and had to exchange. Exceptionally warm, I fell in a brook upto my knee, but these boots still kept me warm in 0 degrees. Love em