I'm very tempted by the bivi's, especially the Dutch one.
However, now that I take a bushcraft mutt with me everywhere it's impractical.
I can't really bushcraft without him, as it was walking him in the first place that kind of gave me the appreciation of the wild that I have now. Plus, the neighbours (and the remains of my flat) don't appreciate him being left on his own.
The cheap tunnel tent I use is bigger (though not as well built and will deffo fail) and allows me to sit up and get dressed etc., and I can get the mutt to move around and warm cold spots.
Using a bivi also reminds me of living under an Army poncho, in a shell scrape with SLR and webbing...
Still want one though...
Eagles may soar, but weasels don't get sucked into Jet engines...
What I lack in decorum, I make up for with an absence of tact.