Good writeup indeed and does show how the experience can be tainted by bad customer service. I agree with most of your points, especially the boot, which is something I am tempted to "mod" when mine arrives. And the paddle getting in the way of the dial
On the engine and gearbox front, you were definately comparing apples with oranges, with a 370z 7AT with only 100 miles on the clock against a remaped 350z. I have driven a 7AT with 4k on it and it was as responsive, if not more, than my 350z with lightweight flywheel and 80k on the clock. I think if you were to drive a manual with more miles on it, you would be much happier with the car. The car will be sooo tight with 100 miles on it, they shouldnt even have let you taken it over 4k RPM or full throttle according to the owners manual The gearbox is lovely and smooth once its worn in too, much better mapped than the G37 which uses the same hardware. The G37 is too smooth, feeling like jelly, the 370z feels more direct. Using manual mode for pootling around does let it down as it makes the changes faster even when not gunning it which can make it feel horrible, the thing to do then is to use the paddles in auto mode if you want to override which gear you are in then it makes a nice smooth change still.
Make sure you post picks of the Cayman when you upgrade though, they are lovely cars