I have used the Black Diamond exstensivly 3 seasons so far. I mostly do multi-day solo hiking trips.
Things I like:
Weight....it only weighs about 18 oz with poles!
Price..is under the $200.00 mark....
Quality of construction. It has held up extremely well to all of my camp set ups in the back country.
I like the extra shaped head room. Also, there is plenty of room above your head to stash a water bottle, flashlight, a pair of pants...etc....
It seems to be fairly water proof, and hasn't sprung a leak yet.
Windproof!
It seems to breath well, with little condensation inside.
I like the bug netting, easy to vent and keep fresh air coming in.
Zippers seem to work good, no problems.
The length of the bivy is good.
The color is easy to spot from a distance, incase you do any exploring from camp.
Things I don't like:
Set up. This is the most annyoing tent/bivy that I have ever had to set up. Yes, it only has 2 poles, but getting them to work together takes me roughly twice as long to set up then a standard 2 man 3 season tent. But once it is set up, it is a gem.
Zipper length. I would like the zipper to be able to zip down a little farther on the side, this would allow a bit easier entry/exit..
Getting in and out requiers some fore-thought and some aggressive yoga moves!
Overall, I dig this bivy alot, and think it is well worth it. It is one of the better bivys out there in terms of weight and room. A shaped head area is the only way to go. I would never buy a bivy without that feature...it would be too clausterphopic to have the nylon on your face all night. I'm a big backpacking light fanatic, and this is the best alternative out there to tents and crappy tarps. It is not perfect but bridges the gap between the 2 extremes of sleep systems, without weighing you down.
just my 2 cents