Now that lighter polyesters and nylons are becoming available, and more waterproof coatings are coming from Asia, it is hard to justify Cuben, especially at the price.
I still prefer woven fabric, so long as it is in the one ounce range like Cuben.
Specifically, GoLite, One Planet, Snow Peak and Mountain Hardwear, are all selling tents now with coated woven fabric well below the 30 denier we thought was the new light when silnylon first became available in the nineties. I plan to try out a couple of these using fabric in the 15-20 denier range this summer to see how they hold up. My gut tells me they will hold up fine, without any of the downside issues with Cuben.
With respect to the weight issue, even using heavier 30 denier nylon, .76 oz cuben with a denser layup of Dyneema fibers weighs about .5 oz per sq. yd. less than 1.28 oz. silnylon coming from Asia with a substantially higher HH, or water resistance. A typical solo tent will use about 6 square yards for the outer canopy wall. So the Cuben saves about 3 ounces overall. With larger tents, the savings is greater.
The chief attractions to me of woven fabrics are the superior ability to hold stitching, and the elasticity that resists punctures and abrasion, while also allowing for a taut canopy.
The sagging issue with nylon can be addressed by using woven polyester, which is less water absorbent, and by using nylon with more water resistant coatings. The sag is also less of an issue in tents with more frame support, whether they be domes or multiple hooped tunnels. Also, some of the paraglider woven fabrics are sub one ounce, and are treated to resist sagging. With better treatments for water resistance, some of these fabrics, like Porcher Sport Skytex 27 for example, would be excellent for tents and tarps.
Cuben may soon be passe.