It is fast by most standards, especially considering they decided to launch a new platform to support this. They could have probably easily used one of their other platforms to build the Solstice, but it sounds like GM knew what it really wanted out of the car, and they knew it wasn't going to cut it.
From early indications, the Kappa platform looks like a winner, and could be a good glimpse at the future in GMs leadership in small volume, niche products. That really is the future of the market, and any manufacturer that can gain a leadership position, while maintaining quality, will be in very good shape. That is surely GM's goal.