The boots are plenty flexible, that's fer sure, on the level of my La Sportiva Glaciers in terms of how soft they are. I think the point about fitting the tab into the cleat is a concern, but that seems a small price to pay for having a comfey boot that converts into a super stiff pair of ice tools for your feet. I'd like to actually try these things out. I'm sure that Montrail will be making the ice fest circuit.
On that note, what's the latest word on Lillooet?