I've only driven one car with paddle shift (F355 GTS) and I didn't care much for it.

To shift, you just pull one of the paddles. The Ferrari system would upshift sometime after you pulled the paddle UNLESS you were absolutely flat on the gas and then it would upshift close to when you pulled the paddle, otherwise it seemed a bit random to me.

If you grabbed a downshift, the ECU would not let you mechanically over-rev the car and would wait until the revs dropped enough to go to the next lower gear. This didn't bother me as much as the upshifting.

I'm told they improved it on the 360's but I've not had a chance to drive one.

I've HEARD that the BMW SMG box is fantastic, but don't have any personal experience with it.