I like it, a lot!
It is relatively low powered for a supposed supercar, but for Audi this has to be deliberate - remember they own Lamborghini these days, so they have to be careful not to tread too heavily on sales of the Gallardo.
The Gallardo has more supercar prestige than this, but then this is going to be a lot cheaper...so if they made it any faster than it is with 420bhp it'd probably rob sales of the Gallardo as much as the 911 (which is what this is primarily pitched at, rather than the more expensive and exotic F430/Gallardo/911TT).
It'll still be seriously quick though - Audi can do lightweight (the A8 is pretty light for its class) and it 'looks' to be a very compact design, which can only help its performance when you think how that translates into weight...