Daily driving the GT is great. In the year I have owned the car I have driven 12000 miles and have experienced the following issues:
1. Drained battery - needed AAA to give me jump. Battery holding only 350CA and needed to be replaced.
2. Radiator fans remain on even after car is turned off. (warranty fix)
3. Small leaks in valve cover gaskets. (warranty fix)
4. Cracked coolant bottle. (warranty fix)
As for resale, unfortunately the car's value drops like a rock. Although, having a CPO warranty remaining when selling the car is a plus. I would imagine depreciation is around $10K a year after the initial 40% depreciation the owner who bought the car new experienced as soon as the car drove off the lot.
Cars with CPO warranty are slightly more expensive, but I think it's worth the peace of mind. My 2014 has a CPO warranty until Sept. 2020, but it looks like the policy may have changed recently to only add an additional year after the original 4 year/50K mile warranty ends. That would mean a 2015 car would only have a warranty until 2020.
There is a 2015 CPO GranCabrio with 32000K miles for $62000 located in Northern California.