I've owned Porsches since 1971 (911T). Every one of them was a manual transmission and the only issue I ever had with the manual was a broken clutch cable on my '71 T. I had to speed shift the car from Philly to NYC, that was fun. The 991 C2S that I have now is a pleasure. The 7 speed is engaging and driving cross country a few months ago, I put it in 7th, cruised at 90-100mph and got 25 mpg.
Quite simply i have found the manual more engaging and I feel in control of the car. The manual tranny keeps me focused on the driving and when I drive my Porsche, that's exactly what frame of mind I want to be in. If I want to zone out, I'll drive my auto tranny suv and can trance out all the way to my destination. Just my .02.