You have to remember 20 in rims are not the optimal size for all around handling. That is why most true sports/exotics general go with 18in standards. Think of it this way how many cars to you see in the American Leman series running 20" rims
I am sure than I could fine something to complain about on any car, but even the thought of owning something like a Zonda would leave me 1000% satisfied.
On the topic of power, the car does not really need anymore than it has. It was nearly 700lbs less than a Murci and is less (I am not sure how much) than and Enzo. It will be as fast if not faster. Furthermore, if you ultimately crave more power and have the money for this car, I am sure Senior Pagani can help you. Remember this car has a very mildly tuned 7.3L V12 that is certainly capable of much, much more power. This is the same engined used in the newest CLK GTR supersport (the Red one) that is rated at 720bhp I believe.