It is a strong testament to how great the M5 is when these speeds can be reached with a sense of confidence. Recently I've been quite surprised at comments from a couple of Ferrari 360 and 355 owners that told me that their cars don't feel all that stable at high speed. I thought that was one of the highlights of these cars.
Indeed, with the proper roads and lack of traffic the M5 doesn't give the driver any reason to slow down from say, 140mph+. It's a true Autobahn burner in every sense of the word.