Just chuck in my 2 pence worth :)
The engine is one of the major highlights of this car, the fact they stuck with a NA V8 is amazing and to significantly improve it's HP and Fuel Consumption with clever things like switching between Otto and Atkins cycle is great stuff, also keep in mind that the confirmed GSF is likely to use an even higher output version of this engine so don't think this is the car maxed out - I'm guessing a 500+BHP min
The weight issues aren't so much from the quality just (IMO) some questionable design choices - for instance to get the best stiffness they used the IS CC middle section for the chassis, total overkill on a coupe (but might suggest there will be a convertible version?) and that stuffed it weight wise from the start, however there are some other little bits like adding a speaker to the steering column to pipe out fake noise like a BMW, I mean why? It has a wonderful sounding V8!
To me the big hitter I think will be the new ISF - stick this engine in the IS and then see how it stacks up - the IS350 was already beating off BMW, Audi, MB etc in US :)