I just got mine in the mail — they’re almost the same thickness/weight as the wool PI tour socks, but are MUCH softer. These are cold-weather socks without being excessive (read: DeFeet Blaze)
For reference, I wear Size 44 izumi shoes, and purchased the Large size socks. They fit fine. I wouldn’t recommend getting the Large if you’re a 42 or 43, though.
Endura BaaBaa Merino Socks (2-pack)