Thanks for the offer, David. While tempting, I actually own a Western Mountaineering HotSac, which is essentially that. 5.5 oz reflective vapor barrier bag. I've used it many times as a bivy. Love it, works perfect. Durability is fine... if handled with care.
The LAND-Shark interested me for the same reasons, in addition to the camo color (not too crazy on fire engine red, I would like to blend in to the scenery), for the high-visibility orange in rescue situations, it's a bit roomier (HotSac is narrow), and being able to use boots inside (I'm a heavy guy and the HotSac probably wouldn't hold up too well with my boots).
Although, I still might be interested in your fabric. What color is it?
As far as the vacuum packing... not necessary - I'd actually want to use the thing! The ziploc IS a nice touch, though.