I tried it last night with a low of 50F and 92% humidity. I was using a 50F down mummy bag and had to use it on top like a quilt to stay cool enough. A light fleece blanket would have been perfect, and/or go with one pad rather than full length. No moisture problems so far.
I hear you about Fall weather-- colder will tell with condensation. I think I'm set for 3000'-5000' hiking for the rest of the summer (doing a little dance).