I own the Accuscreen 106" AT white and think it is an excellent screen. I used it for about a year and found no warping. In fact if Accuscreen made a larger version I would still be using it.
Screen assembly is easy and professional. The frame rails are continuous pieces of aluminum with corners that simply slide into one another with a thumb screw to tighten it down. Once assembled the screen is perfectly square. The fabric material has a plastic spline sewn along the entire length of each edge. This spline pushes easily into a channel on the back of the frame, which holds it very securely and evenly with no wrinkles. If the screen becomes dirty it literally takes two minutes to remove and throw into the washing machine. Four plastic clips are used to mount the screen to the wall, two top and two bottom. These hold the frame from the inside of the rail and therefore prevent any warping from the fabric tension. I suspect that Hound888 either did not use the clips or failed to position them properly, resulting in the observation that the Accuscreen warps easily.
The weave of the fabric is quite fine and very even. From my 9 foot viewing distance I was never aware of the texture. In comparison I find the weave of Center Stage XD very noticeable from this distance. The Accuscreen is slightly less reflective than XD but the color accuracy is just as good. I made no measurements but was totally happy with it's acoustical transparency.
The only aspect of the screen that reveals it's very reasonable price is the stick-on velveteen frame border. It did a great job of absorbing light, but was not fully stuck down when the screen first arrived. After pressing it back in place then hanging it against the wall, the velvet did not lift again.
When I first purchased the screen I searched AVSForum to see other's opinions and was surprised how little information I found. Perhaps the limited size selection curbs enthusiasm or maybe enthusiasts just can't believe that such an inexpensive screen is worth considering. In my opinion, if the size works for you there is no benefit to spending many times more for an over priced competitor's material.
Costco seems to carry the grey version all the time and the white comes and goes. Since building my theater four years ago I have played with various screen materials and combinations of grey and white fabric. In my light controlled room, even with a bright projector, I have found that screens which have a definite greyish tint in the light of day zap too much color and brightness from the projected picture. If your light control is poor then perhaps grey is the way to go, otherwise I would hunt down the white version.