I don't know what experiences you guys have had, but I must disagree with this negative stance on using rubber padding on the mounts.
I've used some rubber from home depot bungee belts, and months later they're still there and work just fine. The engine has stayed in place and I've never had to re-tighten the mounts or change the rubber once.
EDIT: This is what I used:
Just cut off pieces or slice them in half to the size/thickness you need, and they work great.