At first it was a bit rough, but newest update made it an essential plugin for me. Posing is fast and efficient. Also, position changes register with Timeline without need to manually keyframe pose (even if you just copy over sides instead of moving the controller!). Along with nicely working real-time symmetry, animating will be much more efficient in many cases. Below tip for Timeline users, as in one case it can mess up your keyframes.
Having symmetry on will continuously create a keyframe for your right side targets only, but make sure to have it disabled if you are using scrubber with your mouse in Timeline, as each time you select any time position, it will create keyframe there. You could have it on, if you navigate only with next frame or previous frame. Or you could navigate with the mouse with symmetry off and hit the button twice to register a single keyframe where you want it. During playback extra keyframes are not created. But you should be really using either symmetry mode for full mirroring and keyframing only left side then, or using it to create right side mirrors at specific points.