It's interesting you bring that up.. I was just thinking the other day that since my 07 GXP was my 80 mile per day commuter, that wouldn't it be nice to not be stranded in the event of a tire puncture or blow out. I was doing some on-line research as to run flat tires and found very few options on the market. As you pointed out, in the past the run flat tires got pretty well panned by the performance community. I haven't seen any ads for run flat tires in several years, so I figured the idea was more or less half baked anyway.
In the meantime, besides the GM supplied cheesy air pump(tm), I have one of those rubber plug kits in my "trunk" with the air pump. I've become pretty fast at plugging radial tires, considering my wife seems to be good at running over nails and screws with her Fiat 500. In the time it takes me to remove a wheel, remove a potential spare, then put it back on the car, I can remove the sharp object and insert a rubber plug. Plus the plug kit takes up far less space than even a compact spare used in many cars.