Funny, I always smile because of how little it vibrates...
Boxer = smooth sailing, but it's all relative.
BTW it vibrates because it is directly attached to the engine, which has thousands of explosions occurring every second. You may not feel it on other cars because they were developed with comfort in mind (don't let the soccer mom worry about the vibrations from the 300 hp V6 under there!) but sports cars generally don't concern themselves with such trivial things.
tl;dr if something was vibrating in a bad way you'd hear it or feel it somewhere other than the gear shift lever.