I was at the PCT Trailfest in Seattle yesterday, and a FF representative was there with a couple of sleeping bags on display. If I recall correctly, one was a hummingbird model (?) with Nano fabric; he had pooled some water on it some hours earlier to display the water resistance. The other bag was a woman's bag I think, with Epic fabric. From the conversation it was clear that Nano and Epic are different. If I recall correctly he said that the Nano is inherent with the material itself, though I think it also had a DWR (?).
The impression I had at first was that this were truly waterproof, but it seemed like he was backing away from that in the discussion (?). Still, he didn't just pool the water (actually did this on both the fabrics) but rubbed the under-water fabric with his hand to show that even adding that mechanical action didn't allow water through.
My wife and I had recently bought sleeping bags, so I have to confess I wasn't paying intense attention to all of this, but it sounded pretty neat. I can accept that there are different degrees of quality to various DWR treatments, but don't know how to evaluate them either for wearability (need to reapply) or overall effectiveness. Or for that matter, how they effect the ability of a down bag to dry out once it does get wet.