It is compact and light weight. It comes with it's own stuff sack. I use a waterproof bag for it as well. It fits nicely into my kayak. It comes with a ground cloth. And it is available in white - any other color will not be as breathable and waterproof. Thus far, that has not been any problem for me. And the trade-off for some "cool" color is well worth it.
I'm 6-3 and 245 and haven't fit any other bivy sack - the Uber Bivy is like the Taj Mahal. Lots of room, a couple of convenient pockets for glasses, wallet and such. Set up is a snap - two identical, flexible poles slide into the bivy and form a space for your head. A mosquito net or a solid closure allow for a comfortable night either under the stars [and bug free] or snug in your own world. Both work well.
Dave Miles knows what he is about and makes every bivy himself. He only sells on the internet and by word-of-mouth. Just Google - Miles Uber Bivy and/or go to milesgear.com