This was my first bivy and it had nearly everything I wanted. It's small, light weight, east to pack. It opens to fit into a space a couple feet wide and 8 feet long. There's ample space for my sleeping bag a book and a water bottle. There's also good headroom for a bivy. I found it to be warmer in cold weather than my tent. The Gortex really blocks the wind. It cool weather, there's not much of a condensation problem.
I had the problem that many other reviewers had. The pole is cheap plastic. I was surprised that it wasn't something a little stiffer. It would have been great if there was a way to run lines from the the arch to tie points on the ground. This may have kept the top from flopping closed. When the top was closed in moderate (40F+) weather, moisture collected on the inside and my down sleeping bag was damp from condensation in the morning.
This was my first bivy. Even though it's lighter than a tent, It's not that much lighter than some ultralight tents. If I'm going to give up the comfort, storage, and options a tent offers, I opt to get a lighter weight bivy for the summer.
Perhaps I can't get away from my tent. I like to have my backpack in the vestibule to keep it dry, and close by, along with my boots. I like to move around a bit and a bivy is restrictive. I also camp in groups so sharing a tent often weighs less per person than using a bivy solo.
I recommend the bivy for cooler weather camping when you don't share a tent. It's light weight and keeps you warmer than an ultralight tent.