 One thing one needs to accept about this car is that it's not meant to compete on the track against a Cayman S or Boxster S.  It's just not that kind of car.  It's absolutely great for what it was built for, which is to be an enjoyable high speed, top down cruiser.  If you drive these other cars, you will immediately notice how much better they handle, but for everyday driving, the Z4 is quite good.  The N54 engine is superb and eminently chip-able.  The car is comfortable and luxurious.  The only cons I've really identified is that in the 2011 model year, some cars do not come with the Combox controller, which means you won't have bluetooth audio capabilities.  Also, the handling in some tight corners feels a bit delayed.  I've felt the rear end skitter out on me more than a few times.  Not the extent that it would be dangerous or cause any real concern, but it certainly doesn't have the "turn on a dime" feel of those mid-engined cars.