I've driven pretty much all of them, as I have a bunch of local Porsche buds here in the tri-state area that let me drive their cars: 2.5L Boxster with 201hp, 2.7L with 217hp (I own one), 3.2L with 250hp, 3.2L with 280hp(987S), 3.4L with 295hp (Cayman S), Base 997 Carrera Cab with 325hp, 997 Carrera S Cab with 355hp, and 996 Carrera GT3 with 381(hp).
Not counting any of the 996 and 997 cars, I honestly can say that from my experience, there really is not that much difference that I felt between driving my car (an 01 base 2.7 with 217hp) and the 986S with 250hp. I actually could hardly feel a difference in pull during acceleration. The 280hp Boxster S I drove, while a nice improvement in design inside and out from the 986, still didn't wow me with the power delivery. The difference I really did feel was between driving my car and the 295hp Cayman S. That drive really impressed me, and it felt like the car, in gears 1-4, had a real nice kick in the pants to it. I think the best value at Porsche today is the new 3.4L Boxster S. Top down, great looks, fast car, with all the new gadgets.
The Cayman S I drove felt almost just as quick as the base Carrera I drove, but of course, slower feeling than the GT3.
Back to the question though- do I regret not getting the S from the get go? Yes. I happened to first test drive a base, and felt it gave me enough grins, so I decided to buy it right there on impulse. Do I enjoy my car any less because of that decision? No. It's still a heck of a fun car to drive, and I'm gonna keep it for a while. Plus, it's nice not having a car payment when NYC parking costs me $560 per month.
