Well, I'll be fair and qualify what I said. I don't know a stitch about sewing. I use mostly consumer end products made out of fabric. So when asked "what do you like about Epic?" I would say, "It's lightweight and breathable". Yes, I know that's a lot of help. The bivy that I have (the Oware Epic Bivy) uses Epic Malibu on the top and 1.1 oz silicone ripstop nylon on the bottom. Epic Malibu, as I understand it, is rip stop that has been treated to make it water repellent yet retain breathability. The idea, as I understand it, is that rather than laminate all the fibers, each fiber is encapsulated individually. The fabric is very soft and so far works well as the top of the bivy that I have. I think all bivy bags produce condensation. Some deal with the fact better than others. This bivy, with both the Epic fabric and design features, is better than most I have used.
So I can't comment on the fabric on it's own (how easy it is to sew, etc). I can only comment in fairness on how the Oware Epic Bivy performs with this fabric as it's upper.
Sorry if that's not a lot of help.