Nope, the S2000 was great, I've driven SP1's and 2's both on the street and track.
The simple fact that the BRZ is within six seconds of the S2k is very impressive given the tires are a serious handicap compared to even the S02's on the Honda, given that they're nearly identical in weight and torque, with the S2k having a higher rev range and associated hp advantage.
I get the garbage tires being fun in casual driving, and I get that it's easy to remedy this with better tires for those of us that seek track time and higher limits, clearly the chassis is capable of taking advantage of more grip.
I daily drove and tracked a Miata for years, and my last car was an M Coupe with the silly, understeering staggered setup, very similar to what Boxsters wore. Many track rats switch to square setups and I'd likely keep the BRZ that way.
I've seriously considered buying one, I certainly haven't ruled it out (current dealer pricing makes them less desirable), but I'd be very tempted to jack with the power of a stock one, so waiting (semi patiently) for an STI version doesn't hurt me one bit. I'm not voicing displeasure at the current state of the BRZ/86/FRS, only stating that the chassis is clearly capable of more and that offering two versions hurts no one, especially the bottom line.
I don't want a supercharger, at least a non intercooled one like TRD is likely to offer. I live somewhere that it gets hot and track time with an engine without adequate cooling isn't fun.
If I were looking for a 100% street driven, amusing car, the stock BRZ fits that bill very well, but for a car that would be tracked, I'd like the power to push the chassis a little closer to it's limits and not be flat footing the thing around all day long. We haven't talked about frequent discussions of the weak brakes, but that's another area that STI may help, although the Brembo's on the STI Imprezas haven't been too stellar.