I like the turbo noise on the 3 cylinder more than the 2.0 actually. It has a mini blow off valve type sound on the upshifts. You need the windows down to hear it though.Haven't noticed undue vibration on my Cooper, now at nearly 2000 miles. The three cylinder engine has a balancer shaft to prevent its inherent imbalance from being an issue.
I really like the sound of the three pot while accelerating, the off-beat thrum reminds me of other more powerful exotic cars.