I'm late to the thread, but here's my $0.02. I owned a Wiggy's overbag, I believe was rated to 35*. The bag was well made, the temperature rating was within reason and by sheer luck the zippers mated to my REI polarguard bag. I was able to nest the two bags together for winter use just as if I had a second Wiggy's bag. The overbag did what I wanted it to do, that is, keep me warm in the summer and extend the range of my REI bag in the winter. I never got the bag wet.

Along the way I discovered ebay, took a chance on a down bag and never looked back. I sold the REI and Wiggy's bags on ebay and now have several down bags of various temperature ratings from 20 to minus 20. All my down bags are from ebay and at least 25 years old and in great shape and very well made.

The insulation in Wiggy's bags seems to be durable, I think it's basically old school polarguard. The newer polarguard seems to have sacrificed some durability for weight savings, depending upon your point of view the trade off may be worth it.

For me, down is more comfortable to sleep in, packs smaller and weighs less. In spite of the cold when wet issue, I have not slept in a wet sleeping bag, down or synthetic, in over 30 years.

In my opinion, there is nothing wrong with Wiggy's products. Compared to other synthetics they are heavy for their temperature rating, but for example they do use a number 10 tooth zipper and few other companies do that anymore.

There is no free lunch here, everything is a tradeoff of warmth, weight, cost, quality, you have to choose which criteria you are most intested in maximizing. If you choose Wiggy's the quality is fine, but you'll have to balance out the remaining variables as they pertain to your needs.