I bought a Rab Ridge Master a while ago, which is roughly the same shape/size as the DPM one Wingstoo posted.
I fancied a hooped Bivy because of the smaller pack size,low weight and i fanced something low profile with a small pitch footprint.
I had planned to buy a Micro Tarp as an optional bit to use when i felt it was needed in bad weather etc, but i honestly cant imagine me using one of these bags without the added space from a tarp and groundsheet.
The first time i took it out, i never had the micro tarp or groundsheet for a porch area. It was raining, i was wet, dirty and tired, and i was honestly considering selling it as soon as i got home the next day. Horrible experience trying to cook in the rain, get changed into clean clothes and stay dry while standing on wet grass in a downpour. (Unless your a contortionist, good luck doing this inside while keeping it relatively clean)
Since then ive been using the Micro tarp plus groundsheet, which does make things considerably better, if still awkard. But by the time i add all the weight of tarp/groundsheet and extra pegs, and the fact its no longer a quick pitch, id be as well carrying a tent anyway. Of which many are quick pitch and just as light as a hooped bivy.
Another problem i have is condensation. I do get very little, hardly noticeable (with the door open a bit all night) but because the bivy is so small inside, any movement at all and my sleeping bag touches the walls, resulting in a wet bag overnight.
I had bought it for a week long trip in November, over my 3kg Vango tent, but tbh i am just going to suffer the weight of the Vango for the benefits of a bigger living space to make every task so much easier. And i also dont fancy a wet bag for a week
I will still use the Bivy for Summer Munro bagging trips, but im still considering getting rid of it and going for a lightweight tent instead.
The worst part about all of this?
I posted a thread on here before i bought the Ridge Master, and got told pretty much all of this