I don't see what's so special about the RS4 engine. Ok I whole-heartedly commend Audi for growing some danglies and actually meeting BMW head on with a NA engine (witness how they chickened out with the RS6). However it's not a very good engine unless you look at the spec. When I read the brochure, I was like "Wow, off the hizzle fo' shizzle!!!" but in real life it's just not that special except for the fact that it revs like no Audi before it.
The main problem is that it is very linear and one-dimensional. I see no difference in sound or delivery between 5 and 8250 rpm which means that I often shift too early or bounce of the limiter. The engine just doesn't push you to squeeze out every rev like the E46 M3 or a I4 sport bike. Also, there is not that much throttle response, not even close to something like the Ferrari 4.3 or the BMW 3.2 . Also, the direct injection whine just totally ruins the sound. It is weird, on some days I almost don't hear it and only the engine sound, other days their is so much whine, the engine sounds like a blender, complete crock.
It's not an engine with a lot of character. Very competent, but it leaves me cold. I heard the old Arese Alfa GTA V6... now THAT is how an engine should sound and feel. I can only imagine if Alfa had the cash to push it to 100hp/liter.
As for the R8... Audi definetly benefits from lowered expectations and the fact that it's cars are much easier to squeeze performance out of. I think from next year, once Porsche updates their engines... Game over, 911 will be back on top.