I too went to look at RS5 the other day but I came away underwhelmed. I currently have 03 A4 and I just got rid of E92 M3 which I drove for nearly four years. Since I'm a car guy I thought I'll get RS5 while I wait for LCI updated M4.
I do agree that RS5 looks awesome and sounds awesome as well. I test drove a fully loaded model. That's were pros end for me. Interior is ok, nothing special, dashboard is right out of A5 the only things RS5 adds to distinguish it form A5 is a steering wheel (very nice) and shifter. Materials used for dashboard felt very cheap especially hard plastic in front of the passenger. My old Audi has higher quality materials inside it for instance. The back seats are also useless, once I set my seat for comfort (I'm 6' 2") I couldn't fit anybody back there. Front seats are also not as good as M3's, no adjustable side bolsters and they felt pretty hard for such an expensive car. Audi's DCT was also disappointing, there was a delay between paddle shifter input and gear change and I constantly would pull turn signal/wiper/hi-beam stalks instead of paddles...this was annoying. Engine, while awesome sounding doesn't have the urgency S65 has. Last, throttle response wasn't there either. This car was worth about $55K to me and not $80K they want for it.
After I was done with RS5 I immediately put a deposit down on a new M4."