I had the same problem. I had never tried a bivy and wanted to incorporate one into my winter setup. Saw it on the Zpacks page, and thought it was intriguing but couldn't find any info on it at all, even posted here with no responses. Regardless, I decided to pull the trigger on one, and actually used it for the first time this last weekend.
So I repeat, this is the first time I've used one. First, I'll go with the "likes." First off, it's super light, and packs down small. The bug net is optional, and just velcros off. I didn't use this option, since bugs aren't a problem right now. It definitely boosted the temperature in my duomid. I experience a little bit of condensation, but it didn't bother me at all. And now for the "dislikes." It's kind of a snug fit for me, I'm about 6'1" and 200 lbs, and sleep mostly on my side. It was tolerable, but I toss and turn a lot, and it was kind of tricky. Also, it's not fully enclosed without the net, which probably isn't a problem, but sort of lingered in the back of my mind.
Hope this helps/makes sense. I'm typing this on my phone. If you have any questions that I didn't cover, which I'm sure you do, feel free to ask and I'll do what I can to help.