I have a OR alpine bivy that I have used a few nights. It worked well, had temps in the low 30s with the windchill dropping it into the low 20s and rain throughout the night. Bivy really cut the wind and I woke up dry. I did find the clamshell opening hard to get out of without dragging my bag along with me. Also, at over 2lbs, it is one of the heavier bivies. Some of that weight can be saved by forgoing the pole.
I just bought a Bugaboo II that Bill was selling and can't wait to give it a try. It is almost half the weight of the OR, and seems to be very well constructed. It has a flexible wire sewn in to keep it off your face, saving the weight of a full pole. The opening seemed to be better designed as well with a T shaped zippered opening. The zipper is about neck level, meaning that the head of the bag should be trapped as you get out.
Overall, I am pleased with the OR, but think I may like the Bugaboo a bit more. We'll see once I get some forest time with it. I am planning on keeping both though, if that says anything.
I bought a borah Event bivy this year only used it for 5 days but I like it a lot temp range using it was mild snow to 50deg at night and I didn't experience any condensation but I slept with the vent open also so I wasn't breathing in the bivy if you decide to go with the borah the double zipper length is worth the extra $10
I have a Borah bivy as well and like it a lot. I didn't have any condensation issues like I have with others in the past. They have deals on the every now and then on massdrop too.
I used the borah bivy this year. It's event. Has a side zip. Cheaper than other events. I really liked it. Lots of room held up well. No complaints. I would recommend
I used the bugaboo II this weekend and loved it. I slept with it fully zipped up at times and did get some condensation right above where I was breathing. The amazing thing was that I would feel the condensation start against my face, but by the time I reached a hand up to touch it, the moisture evaporated. We were also getting gusts of wind up to about 25mph throughout the night, but the bivy blocked it very well.
I would like to point out what great customer service I have received from John at Borah. I ordered an eVent bivy and I need it by early this week. John emailed me and said he upgraded my shipping for free so I would have it in time for my elk hunt. I can't speak to the bivy itself but the customer service has been very impressive!