I daily drove mine for 2 years. It is fine, but there are a couple of factors. Your S5 was a Luxo cruiser. The Porsche is much louder on the highway - it simply has less insulation. It is much more responsive. And much more fun. I had numerous things replaced on mine, all under warranty. Could have been simply my over zealous dealership. (I've been meaning to start a long thread questioning real 997 reliability). No doubt though, ,the reputation is excellent.
Getting a C4s will make the car awesome in the snow with snow tires, but ask yourself, will you really take your baby out in a snowstorm? I sure didn't. I ran all seasons in the cold and avoided most of the snow and was fine all the time. The all seasons gave perfect traction when it was cold and I generally avoided the snow. I'm not driving around with idiots in Camrys and bald tires in the snow. Also keep in mind you're driving a snowplow! Many others have had no problem in really snowy climes though. Be sure to drive a C2S as well, they drive better and 2wd is not bad in these cars. (remember that the main thing for snow traction is having the weight over the driven wheels).
Also, biggest factor - mileage kills the resale on these cars. My car had over 30k in the end and is a VERY hard sell, even for an 07. Sure, great daily drivers, but nobody wants them if they have miles. There are too many garage queens in the market to compete against. So, if you want to daily it, you're really going to pay for it.