I bought the 30 degree Sierra Design Dri Down bag a little while ago quite discounted, and about 3 weeks ago, when hiking in the Shenandoah/Blue Ridge VA area tested it out. The weather forecast called for a clear night for that area, and since we weren't that high up or that far into the "mountains" yet, i thought it would hold true for where we were.
I had also brought my homemade tyvek tube tent, which is really only a 1 p size. I was going to cowboy camp for the night and let my wife sleep in the tent--for whatever reason, i decided against it when it was still clear. It was unusually warm and humid that night, and then the fog and rain rolled it. I hadn't found a fully level ground to pitch the tent on and so we would slide down the tent a bit on our sleeping mattresses (i need to do some silicone dots or something).
It was sucky, wet conditions, and i was surprised at how well the bags did despite the very, very high level of humidity, the condensation that was dripping off onto the bags, and occasionally sliding the bags out into the rain a bit (thankfully the rain was light). It kept very lofty (well, as lofty as 600 fill is going to be, wish they had a better quality option). This was only a weekend trip, and when we got back, i threw the bags into the drier and they seemed completely dry after about 20 or so mins. on low/medium heat (they had probably dried out in the car some too, since it was quite warm and sunny the next day).
My question is, how long will this last though? If i hadn't gotten the bags quite a bit cheaper than their regular prices, i probably wouldn't have bought them. I sold my new Golite Adrenaline 40F + bag recently--certainly miss the compactness and low weight.