I have a Double Rainbow which I purchased for hikes with my wife. It replaced our original Tarptent Rainshadow, which we used when our daughter came along. (She's in college now, and when she comes on a hike, she steals, er, borrows, my hammock.)
The D.R. is my third tarptent, and it's a good one. Very well constructed, and quite wind resistant especially if you use the optional hiking pole supports down the middle of the two doors. I've had it in 30-40 knot winds and it held up just fine. I particularly like have two doors on the long side walls, much better than the tunnel entrance of the Squall and the Rainshadow, in my opinion. Better ventilation and much easier access.
However, in the D.R. design, the long side walls angle in toward the top, greatly reducing interior room. We kept bumping into each other. After a year of trying to make the D.R. work, we purchased a Six Moons Designs Lunar Duo. (My sincere apologies to Mr. Shires.) That tent has significantly more interior room, at the probable cost of some wind stability. We haven't had it out in the wild yet, but we're looking forward to it. Like the D.R., the Lunar Duo has two doors, two large vestibules, a "bathtub" floor, etc.
As for the Double Rainbow, I had it on an eight day solo hike in March, and loved it as a solo tent. Having both doors wide open gives incredible views and ventilation, and it's easy and quick to set up and take down. So I'm keeping it for solo hikes when I want to take a 3+ season tent.
Finally, I just wanted to say something about durability and storms and all that: the above responses are right. Unlike in mountaineering, on a thru-hike one rarely needs to worry about camping in an exposed area. None of these very light tarp-tent designs will handle serious exposed mountain weather without help, but that's not their intent.
If you like the Tarptent shelters, but you are still concerned about stability, take a look at the Scarp 2. You might like it.
http://www.tarptent.com/scarp2.html