The bottom line: This is a great bivvy for good weather camping and ultralight hikers. While it's not the lightest bivvy available, and it's not the most weather-resistant, it strikes a nice balance between the two and is ideal for hikers who want to shave some weight off their camping equipment or want to add a few degrees to their sleeping bag rating but don't need heavy-duty protection from bad weather.
I did lots of research before buying a bivvy bag. I'm not really an ultralight backpacker, but I did not want to have to carry a heavy tent when I camp alone, and I didn't want to spend hundreds of dollars on an expensive ultralight tent either. I finally settled on the Hunka XL bivvy bag, which is a great bivvy for my uses - which is mostly single-night, good-weather camping trips.
Alpkit doesn't try to fool anyone with the Hunka XL - they admit that it is not 100% breathable, and it is not 100% waterproof either. Practically no bivvy you can buy will be - nearly all bivvies have condensation problems. But with the Hunka XL I've only encountered very minor condensation problems, and only when the temps get down to 35 degrees F or below. And for one-night camping trips, this isn't a big deal anyway.
The Hunka XL will add about 5 to 10 degrees to your sleeping bag's rating - so a 30 degree F bag is more like a 35 degree F bag. I have slept in it in light rain comfortably, but really heavy rain will ruin your night in this bivvy. If you often camp in bad weather conditions, you'll probably want to get a more substantial bivvy with poles or a tent.
The Hunka XL weighs only about a pound and packs down smaller than a waterbottle. It's quick and easy to set up, and it folds into an attached drawstring mesh pocket for easy storage. Despite the small packed size, there's more than enough room inside the bivvy for a sleeping pad and a thick sleeping bag. Alpkit also sells a smaller version, the Hunka, for those who don't plan to use a sleeping pad.
Though it is light and relatively cheap, the Hunka XL does not feel cheap. The seams are taped, the build quality is good, and I don't worry about it ripping or tearing even when sleeping on rough ground. The head opening also has a drawstring if you want to seal yourself off completely in rain or cold.
The Hunka XL is always in high demand and frequently goes out of stock on the Alpkit website, which is the only place I could find it for sale. You can request to be notified when it's back in stock.
All in all, the Alpkit Hunka XL is a pretty simple product, and there's not much else to say about it. As a cheap and lightweight good-weather tent alternative, you can't beat it.