http://www.bmwe34m5.com/faqs/
Have a look there too.
They are a fun car to drive, however, owning a V8, and driving friends ones, you have to drive it like a sports car (high in the revs) to get the most performance and fun from it. Not an ideal daily driver. 315hp and less torque the the 540 (obviously). As a real performance car, the E28 M5 has a better power to weight ratio and is rarer.