Went out in a spring downpour with my Carradice 2 weeks ago. My riding partner was wearing his as well - and we both commented on how relatively pleasant it was - we did about 15 miles in the rain and road mist, then it started to dry up for the rest of the ride. We did fight a headwind - so we were fighting the capes - but we were dry and not riding in a sauna...
I like the duxback cape - its heavy - but it stays put on the bars. I'm cutting the hood off of mine - just a bucket that collects water - and while it is useful when I ride around town without my helmet - it doesn't fit over mine.
I like the hand loops too - but find that with the duxback I don't always need them.