I just got back from the dealer. I drove my car again and was able to better isolate the problem. When the clutch is in its top 1/3 of travel (from neutral to just before it engages), you felt all kinds of weird vibrations, particularly when the car is moving and you're shifting gears. I got my service advisor and the shop foreman to drive the car, then they drove another Z3 for comparison. The foreman's theory is that one of the clutch plates is warped. So, that now means I've twice driven my butt up to the dealer only to drive back in the loaner car again -- two hours round-trip, duking it out with rush-hour traffic.

(Footnote: on the phone, my service advisor had said that he'd driven the car, and so had the shop foreman, and they both said my clutch was the smoothest one in the dealership. Lying bastard.)

The J.D. Powers numbers are interesting. They seem to say that, if I really want to buy something that's likely to "just work" and is sufficiently zippy that I should buy a Lexus IS 300, an Infiniti G35 Coupe, or an Acura CL Type S. Heaven only knows whether the RX-8 will turn into a disaster or not; I've heard horror stories about older rotary engines.

Or, maybe I should just say 'screw everybody', get a Hummer, and double park in the compact car spots.