Well, my set just arrived. First impressions are good. The headset (not inc the breakout box) tips the scales at under 320g, so significantly lighter than the non-carbon older designs. It's comfortable too, but I won't know much more until I go flying on Monday.
I'm not best place to do a credible review as I am only 6 hours into my PPL, but my instructor is interested in getting a set to replace his sennheisers and we should be able to directly compare them to the passive David Clarke set I've been using until now.