One of the drawbacks of some bivi bags is the hole in the top. If you're using a tarp then you don't have a problem. If not, then a bag you can fully enclose yourself in makes sense as it'll keep the rain and flying/biting things out. Whilst a fully enclosed bag will give good protection it may lead you to think you've died and are now trapped in a body bag ... step forward the hooped bivi. This one from Snugpak may offer the best of both worlds. It has 2 pre-bent aluminium poles which support the 'roof' giving a surprising amount of room above your head and chest so you feel far less trapped once inside. It takes around 2 minutes to erect from stuff sack to home sweet home. You can forsake the poles and use it just as a normal bivi bag if you want.
There are 2 midge proof vents, 1 at the front and 1 at the back, both with storm flaps. You have the option of leaving these open on clear nights but you can keep the midge nets in place if you're getting eaten alive. The vents also mean condensation shouldn't be an issue.
It's never going to be as light or pack as small as a more basic bag but that might be a sacrifice you're willing to make. It comes with 7 very heavy steel pegs which help to push the weight up to 1.3kg. Substitute these for something else and you should be looking at an all in weight of around 1.1kg. Put the poles somewhere else too and you should half the pack size. Quite a few hooped bivis exist but most are much more expensive, often over twice the price of the Snugpak.
Is it any good though? I don't know yet, I'll give it a try and if I survive I'll report back.