everything vibrates in my car with a solid mount...i have a nice smooth idle but it makes the car shake to buggery. i compensated for this by increasing the idle speed and its marginally better - but when driving you can hear different parts of the car resonate with different rpm's.
...not that im saying i'd change it - its tightened up my gear changes a good bit, and stopped any excessive movement - but it does make the car a little rougher.