Since you didn't say Boxster S, it's definitely an arguement. The Audi I throw out right away, since my drive in one wasn't impressive. Not enough power considering it's price, the awd didn't seem to really improve things (just remove some fun factor), and the interior is like sitting in a cave when the top is up. The chassis tuning is geared towards safety, not serious driving, so it's not my kind of ride at this price level.
The Beemer has a nice torquey engine, but it just doesn't come alive with revs the way I like. Don't get me wrong, I like effortless speed, but the motor is almost too smooth in it's delivery for my liking, as though it lost it's soul somewhere along the engineering path (a fault I think most BMW motors have, but I'm virtually alone in this regard). The chassis isn't at the level of the Boxster or S2000 either, but it's certainly fun to drive, with tail out action only a throttle blip away. It is one of the better looking cars here IMO, having the classic long nose/ short rear deck the original roadsters must possess. Make this a solid second choice, tied with the Boxster in overall appeal and performance for the money.
The Boxster's styling doesn't suit me, it's nose is completely devoid of character and the interior is below German standards. The engine needs more power (addressed fully in the Boxster S), but the suspension is damn near perfection. Nothing in this class has quite the reflexes of the S2000, but this one has better manners combined with nearly as agile handling. If it was about 10k cheaper, it would deifnitely win.
The S2000 needs a bigger engine by about .5 liters and probably a couple more cylinders, if it's to be truly world class. It should also have a proper glass rear window (cars costing nearly 10k less have rear glass), and the damn dirty digital guage cluster MUST go. But that's about it. Some may fault it's looks, but certainly the beauty of this car lies in the drive. No current car sold in America has quite the agility of this one, and when a competent driver wrings it's neck it rewards like few others. Really, the only unfortunate thing about this car is that you must drive it like you stole it to think it anything special. It feels as docile and reliable as a Civic when driven at anything other than 10/10th's, and does the daily grind a bit too good for a true performance vehicle. Credit Honda for this one, a common genetic trait apparent in anything they've made (aside from perhaps the "R" cars). In terms of performance for the dollar and plain ol' track worthiness, nothing beats it right now. As soon as they address the lack of torque, the car will be a hard one to argue with at the track.
Just my 02 cents
