So to get back on thread topic - Don't buy a tuner and then debate whether to use it or not. Your warranty will be voided and you are much better off debating whether to void it and use the tuner without a $400 unused tuner sitting on your table.
I think this thread has gone off topic lol. I ha my doubts, but as I stated, I agree w most reviewers of this particular product. Car feels "tighter" and stronger. As soon as you step on the gas, there is a transfer of power.