I think the 997 got a big jump start on the r8,if you read the original post on the m5 messageboard (the guys who organizd the race) you'd see the r8 lost ground initially but then the gap was a constant.The 997 driver had also turned all his aircon off and stripped a few things out.
You can also see videos of the r8 beating a 997 c2s w/powerkit ,but more pertinent try and follow an r8 in any porsche round a track and you'll be struggling...top gear twice spun 911s trying to keep up with the r8.

I went from a 997 turbo into my r8 and yes it is noticably slower,but it is so much more fun to drive its not true.
The r8 has moved the game on,even the 430 I drove the other day was not as much fun.