I have a 7x7 Tyvek Tarp and it really impresses me. I only use it as a common area, or a gear tarp (sometimes as a gear hammock). I know Cuben is all the rage, but Tyvek seems damned near indestructible when used as a tarp (as a groundcloth, not so much).
The link below shows a comparison between Tyvek and Typar. I was wondering if anyone had any experience with Typar for tarps, groundcloths, and camping, etc. It sounds like a superior product to Tyvek, in many respects.