Originally Posted by Team Plutonium
Love the looks of the R8, but that V8 is outdated, and has mediocre performance. The only R8 that would tempt me is the V10 one. A supercharged M3 will beat the crap out of any stock V8 R8. But it sure looks awesome.
My buddy has a video of my non SC'd M3 whipping on his V10 R8 Spyder at the track. The car is not all that impressive and it weighs almost 4000 lbs. Its 430 lbs heavier than my M3.
On the way to the track, we found a very desolate straight away, my car (putting out 404 RWHP), 2009 M6 Vert and 2011 R8 V10 Spyder, all within 1 car length of one another.
R8's aren't all that impressive except for how they look. Then again, this car was a spyder, much heavier than its coupe counterpart. But I do see the OP's main point of diminishing returns. My good friend with the R8 V10 said something along the same lines too.
My dream supercar to own one day will be the McLaren F1, Carrera GT or my very own bespoke car.