Yo beat - it's an M45, not a G45. Since you recently drove it, you should know what you were driving. The G and the M are both rear wheel drive too, by the way.
Never driven one yet. Haven't even been in to look at one, but I can already tell you i'd take one of those over a BMW, or any American car any day.
That's my opinion, based on my experience. If I wanted to spend the money on a supercharger, I could be at 375 hp in one day. But why bother? It already goes a lot faster than I should be driving it. Period.