Hi Ducktapeguy,
I would have to agree with most of your comments, a lightweight tent is definitely a better choice.
For a review of the who and why anyone would use a bivi bag
http://www.planetfear.com/article_detail.asp?a_id=425The difference between the ubiquitous orange emergency survival bag and a Goretex bivi can make the difference between life and death. There has been a case where two mountaineers in the Scottish Cairngorms during winter found themselves over night on the plateau. Each were equipped individually with an orange polybag and a Goretex bivi; the one with the orange polybag died from exposure whilst the one with Goretex bivi lost a few toes.
Orange Survival polybag ; 400 grams
Goretex Bivi ; 650 grams
Single wall survival tent (Vaude Refuge); 980 grams
Proper Single Man Tent (Hilleberg Akto); 1600 grams