I'd never put a turbocharger on my BRZ. The linear, quick response is a perfect match for it's chassis setup, and it is surprisingly responsive in the lower end of the revband, thanks to direct injection. People with forced induction cars go on and on about how slow it is...but it really does not feel slow when you're driving it. Acceleration-wise, it's pretty comparable to a stock, 2002 WRX, but with a much more even torque curve.
If and when I ever decide to make it faster (no immediate plans), I'd look at the supercharger, so that throttle response might remain good.
But..at the end of the day, if you drive the FR-S/BRZ, and you're spending your time flooring it on the highway, you've missed the point of the car. It's a surgical canyon carver.