It is hard to describe the sound and I have not been in an M3 to compare. I have an E92 330i and to be honest you don't hear the engine a huge amount unless you give it full beans. My old E46 330ci though.....different story :-)
My E46 330ci sounds pleasent with some throttle action, but nothing like my previous.
E36 320 with the addition of a Scorpion DTM style twin pipe. And my commute at the time included the Blackwall tunnel and the Limehouse Link - Sweet....
I also have an E46 330i and it does have a great exhaust note, especially once you pull and plug the vac pipe for the exhaust valve (golf tee mod). It ain't no ///M though...
I think if anything it sounds slightly better as you don't get that weird raspy bag of spanners in a washing machine thing going on when you nail the throttle as per M3.