Sorry to revive an old thread, but I just test drove an M104 (2.8) and an M103 (3.0) back to back, so I have some thoughts to share.
I drove the 103 first and it gave strong linear acceleration. It builds speed in a very even and proportional fashion. All very proper and Mercedes-like.
But then immediately driving the M104, the difference was staggering. It wasn't just the power difference, it was the whole characteristic of the delivery. The M104 is so eager to go. If you're not careful modulating the accelerator, it'll jump forward off the line without trying! But that's not even the best part. My favorite is the delicious growl it makes when it comes on the cam. I was immediately hooked. (I'm an Alfa guy, so I really appreciate cammy engines)
I can only imagine how the extra 400ccs of the 3.2 would feel!