If I'm not mistaken, the new Camaro is build in a completely new plataform designed for the car(correct me some one if I'm wrong). This plataform was made for performance, and to kill his older and sluggish competitors (Mustang and Challenger).
I find the new Camaro to be a very well ballanced car, and dare to say that it handles even better than the Z06 Corvette, even though not being faster.
I've read in magazines how the Camaro completely outperforms the opposition, so I think they got it right. I was surprised too, as a matter of fact.
The Mustang will never beat this generation of Camaro when it comes to handling, since the Mustang is still running on a very old plattaform not ment for cornering performance.
Here's one article I found from Motortrend which lists all performance specs for the Mustang, Camaro, and Challenger. The specs are on the last page if you don't feel like reading all 7 pages.
As why the Camaro is faster than the M3? I think it's handling is on par with the BMW, but the extra HP gives it the advantage.