In reply to John Newbiggin:
I used the Rebel Ultras for Scottish winter last season. Found them plenty warm with the heaviest weight smartwool socks. Held up better than my mates Nepals on a long, wet and windy walk in / out at Liathach. I'm sure heavier boots will be warmer but that's the trade off you make for comfort, precision etc.
Couldn't be happier with mine and would recommend. Wouldn't get the pro due to lack of gaiter personally.