I borrowed the D38 bag from a friend to try on an overnight camping trip a couple of weeks ago. The attachment straps worked very nicely to affix to the bike. I ride a sportbike and the other dry bags I have aren't like that. The inner liner makes sure that the bag is attached the same empty or full, plus you can add/remove items from the bag without having to re-attach it to the bike.
As mentioned earlier, a wider opening would be nice. The roll opening is a different material from the bag & makes folding it much easier than if it was the heavier bag material.
I'm really tempted to buy one, perhaps even the set.
If it ain't fun, I don't do it!!!
Stuff - I need more Stuff....