I have one teamed with an HPA subframe mount and stock engine/trans mounts (for now).
It really improved the driving but it causes a rattle and lots of vibrations at idle, especially low idle. For some it may not be bad, but I hate it along with my wife. Everyone that gets in when car asks what's wrong with my car so it's noticeable. In fact, I've even had people in drive thrus and friends that were around my car as it sat and idled and asked the same question.
The moment the car gets above idle it's great! I'm having my tuner adjust the idle speed up here soon to see if that will relieve the problem. I keep getting told it's coming from the spherical bearing.
Ac on or off but it's worse when on. In reverse the dash trembles and rattles for a moment and then goes away.