I've driven multiple ones. They are by far the best GM I've driven with the exception of C6 and C5 Z06's (never drove a normal C5, but have driven numerous f-bodies, CTS-V, etc). They are stiff, but unlike most GMs they actually feel composed. I personally like the GTO and would seriously consider one if I didn't want a roadster instead.

The GTO is certainly not a sports car, but it's a pretty nice sporty GT car.

If it wasn't for the interior build quality I wouldn't even consider any european rival over a GTO, probably no japanese rival either. Of course, I don't consider the S2K and GTO to be "rivals" either.