i don't know if it's going to work differently on the e60 than on the e39, but there are a couple of threads on the e39 board about putting a rack on an m5. i have one myself, for my mtn bike exploits.
for the e39 there are two choices: the bmw rack and a 5 series specific thule rack. i bought the latter as it gave me a lot more choices of bike attachments--i don't like taking the front wheel off, especially with disk brakes, and the attachments i got also don't touch the bike frame. both racks for the e39 mount in the roof mounting bolts hidden by small flaps...the rack does not touch the car anywhere other than the mounting bolts. there is some added wind noise (quite a bit actually) and in my case i also got the thule wind fairing which helps, but does not eliminate the turbulence.
here's a link to the thread that helped me decide, with some pix:
Bike Rack
hope this helps. if you have any questions feel free to pm me...
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2011 E92 M3 Space Grey/DCT
05 subi legacy gt limited wagon
98 toyota sienna
06 jetta 2.0t dsg
05 ford f150 fx4 (my daughter's)
specialized s-works fsr stumpjumper
bmw q6.s mountain bike
trek madone road bike
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