I just fancied a change for the most part, although if the paddle shift steering wheel wasn't available then I would definitely gone for the manual option as I hate the silly buttons. Given that the dual-clutch 'boxes are going to become the only option on sports cars before too long to keep emissions down, I wanted to jump before I was pushed and had no say over the choice, plus the PDK 'box is as good as any out there. I've also got a degenerative back problem that gets worse through left leg use, and while it's not a huge problem on a long run it's starting to play me up when poodling through traffic, so having an auto option is proving a godsend (not that I've really had much chance to use it yet). I fully expect to leave the car in auto mode for 90% of the time, however when the mood takes me I shall flick it into manual and it'll be like a different car.
Plus having paddles is like being in a race car, and there is nothing cooler than that!