In the January 2006 Issue of car and driver there is a comparison Between the BMW M5, Cadillac STS-V, and the Mercedes-Benz CLS55 AMG.

3rd Place CLS55
2nd Place STS-V
1st Place M5

Both the CLS55 and M5 got 0-60 in 4.2 seconds
BMW M5 did 0-100 in 9.4 seconds, and 1/4 mile in 12.5 seconds@118 MPH
CLS55 did 0-100 in 9.8 seconds, and 1/4 mile in 12.6 seconds@114 MPH.

M5 got 0.89g's in the skidpad and did something like 65.7 Mph in the emergancy lane change
CLS55 got 0.93g's in the skidpad and did something like 63.5 Mph in the emergancy lane change
M5 had the best Braking numbers

STS-V was behind in all performance numbers.

car and driver gave the M5 a 10 for handling and a 8 for ride
and the CLS55 got a 7 for Handling and a 8 for ride

M5 did very well in this comparison.