It appears that BMW could have went with the AMG philosophy and shoved the S62 - as Mercedes has done with the M156 (6.2L V8) and numerous models - into the M3. By basing the S65 V8 on its bigger brother the S85 V10 we are the recipients of the newer techhnology (for the time) a higher revving, higher horsepower, lower displacement masterpiece.
That being said the S62 is no slouch, and still very much relevant -
http://www.e90post.com/forums/showthread.php?t=795884
3 S62 engined DP cars took the top three starting positions for this years Rolex 24.