having owned a few cars, only 1 didnt have a cat. the only reason why i didnt put one in because i really liked the raspy sound and the nice flames
i agree about the envinronmental issues, yes they are bad. and we really should do our bit........ however like O2 sensors, cats have a life of up to 100k (i think its around that) but like craig already said, no one changes them.
however, there is more of a 0.1% power drop. its more like ~3% just stirring mate!