2009 Mercedes-Benz C63 AMG

Pros: Gut-wrenching acceleration, stable and poised
Mutliple ways to access same function (for driver and passenger)
Harmon-Kardon system and user interface
Room for 4...although those in the back sit are a bit tight

Cons: Rough on fuel...but that isn't a hidden drawback (well advertised)
Trunk could be a bit wider--golf clubs need to be angled in
Tirewear seems quick...couldn't spin tires much early on, now they break loose easily.

Summary: I've owned 9 cars in the last 8 years, 5 of which were "sport cars". I've owned an Acura RSX-S, Honda S2000, Nissan 350Z, Subaru WRX STi, and now the C63...and it is by far the most exhillerating. It has the Acceleration of the STi (and then some), where you are thrown back in your seat, the steady pull of the 350Z (and then some), the cornering that the S2000 had (although the S2000 seemed to grip just a bit better), and the plush interior of the Acura (and then some).
One of the best features to me is that, unlike in my Altima 3.5SL I had (which wasn't a sports car by any means), my wife can access all of the menus and even make the bluetooth phone calls from her seat. Most cars shut off use of those features, or put the controls where only the driver can access.
Also, I really like the sound system. The surround sound is great, and while you obviously can't watch a movie while driving, you can listen...and the soundtracks come over the Dolby 5.1 just fine!
I would like to see a bit better gas mileage, although with 451hp and 443 torque, it's obvious that the fuel injector is constantly injecting fuel...so I suppose that to achieve the acceleration and speed numbers it does, fuel consumption will suffer. Also, the trunk is a bit tight...I have a normal size carry-bag that I use, and I have to angle it in...and even then it barely fits.
In the end, one of the coolest things is that only true autophiles know this car, which means I get punks who don't know what I've got that try and pass me in turn lanes, etc....too easy. I've smoked everything from an Evo X and Lotus Elise to a Mustang Cobra...without much blinking...just be aware that if you have the ESP turned off, you may get a lot of wheel spin before it really digs in and takes off (and if your front wheels are turned a bit and you accelerate, the back end is most definitely going to come loose! What fun if you expect it.