I have been on Dynafit bindings since I began skiing a couple years ago. The first set was the Radical ST, so I felt good about changing to the Speed Radical when I got some new skis because I preferred using a leash to brakes when in the backcountry, and the fact that the Radical lets you skin with your boot flat to the ski as well.
A year on, I have been reasonably happy with the Speed Radical bindings. There is nothing that stands out to me as a drawback to them other than the weight (I recently purchased the Superlight 2.0 and that binding has changed my mind about binding weight...).
It seems that the rotation pin has been a problem in the past (I have the 15-16 model), but I haven't had any issues with them. Also, I've had no problems with the 'rotation issue' so far, but have spent more time area skiing this winter because my son has been learning to ski as well.
All in all, it the Speed Radical has been a solid binding for me. I'm certainly interested in the Plum Guide and the G3 Ion, but until I get some new skis, there doesn't seem to be any reason to mess with something that works - which the SR does...