There are so many cool features about this fly it is hard to know where to start. My favorite is perhaps the least obvious: the awning over the door. It is molded to stick out and let in air with the door zipped down a little. As anyone who has been in a storm on a wall knows, often the biggest challenge is keeping water out while maintaining enough ventilation so your own sweat doesn't built up moisture from the inside. This awning does the best job I have seen of allowing ventilation, even when it is raining and snowing.
The other cool features are small on their own but add up to making this fly awesome:
- bomber clip-in point and intuitive labeling so you know what is the air side and what is the wall side
- plastic windows so you can see what the storm is doing outside
- attachment point for a tent pole to keep the fabric tensioned and not blowing in on you, thus increasing the interior space
- compression stuff sack for the fly (this thing is BIG)
- bomber reinforced corners with clip-in points to anchor the fly from below during windy conditions
I tested this ledge while helping Tommy Caldwell try to free climb Mescalito. When a spring storm arrived I was a little nervous; I had never been in a big storm on El Cap! But this thing was so bomber I didn't want the storm to end it was a nice 36-hour nap fest. You can read a trip report on that Dawn Wall free attempt with Tommy Caldwell here. Below is a video with TC inside the rain fly.
There is not much negative about this ledge other than all those features adding up to make it pretty heavy and expensive. Also, the floor is not very tight under the ledge. This means that when something falls between the big hole in the corner of the Black Diamond Cliff Cabana Double (which happens a lot), it disappears into this big catchment for random small stuff. Not a big deal, but that was one nice thing about the old A5 fly: how tight the material was on the bottom. One minor last point: the material that the stuff sack is made of is not that bomber. I would not recommend hauling the fly outside the bag unless the pitch route is entirely overhanging.
This is one of the best flys for winter ascents or expedition climbing.
For all those features, you have to pay top dollar. This is the most expensive fly out there, but it is the only fly with zip doors and wrap-around coverage. So in that sense it is your only option if you want a burly bad weather fly.