I agree with Lordred... if you get bang on shifts, you need to finesse it more when shifting. I find that while the car likes to be driven fast it does not like or really need to driven hard. Fast 0-60 mph sprints or 1/4 mile times are not what it is made for. It's best suited for curvy road or track conditions. What the car really needs IMHO is a limited slip differential. Get one and you probably won't feel the need for a stiffer rear motor mount. LSD's will reduce wheel hop and spin on harder launches (Again not what the ST does well or is intended for) and better traction in all conditions. An after market rear motor mount can also introduce more noise, vibration and harshness. A good LSD will not increase NVH.
I think everybody goes for after market motor mounts for the wrong reason though. They only seem to solve the problem but what they really needed is a LSD to really solve the problem. LSD's cost more to buy and install by quite a bit though.
Yep, I didn't get any banging on my track day Saturday, and I put in 44 laps on Streets of Willow, progressively pushing harder and harder as I became more acquainted with the track. I will say OE tune pulls real well from 3k even in 3rd