In reference to the Speedtech arms, I really wanted to try them (i've been pretty happy with speed tech products and i'm running their complete front and rear suspension aside from Currie lower trailing arms and my own custom uppers). the price was just too high, but I do like the design. As Gerry mentioned though, it would seem like the uppers would still need some type of flexible/articulating joint, and in that case i'm not sure I see the benefit to the twisting action once you do that. I was also a little worried about the actual twisting mechanism itself on my car with a hopped up LSA and some big tires. I haven't been able to find anything detailed as to how the mechanism works, so I was a little worried about it handling 700whp launches in a 4400lb car.
another variable to throw into the mix is the upper arms would probably function a lot better regardless of what bushing you use with a watts link added into the mix. Having a lateral axle locator eliminates the dual function of the upper arms and leaves them only having to control pinion angle. Even if you use two rubber bushings in the uppers then, you obviously will get some deflection on launches which will affect pinion angle but as far as handling goes, the watts link would be doing all the work so deflection while cornering would be non existent.
A watts link was the final piece of the puzzle I wanted to add to this car but the project got too big and I just want it running now. Plus, the car is already pig heavy with a GM LSX block, LSA blower, boxed chassis, dynamat, 5 gallon water tank, stretched wheels and I couldn't stomach adding more weight