I've had a vert for the last 7 years - and where I live winters aren't bad - they are just downright miserable. We make up for it with some of the most sun of the country and very pleasant summers. As others have said there is nothing like driving around with the top down enjoying summer. I would never give it up and during summer the top is down 90% of the time.
As for V6 vs V8. If you plan on keeping the car for a long time seriously consider the V8. My old vert had the V6 (although the rather pathetic 192HP version) and after a few months I regretted not getting a GT. When I bought my 2011 it was GT or nothing. Drive it easy (if you can) and you will get decent mileage. Get what you want, but don't let cost be the only deciding factor. How often does a person buy a brand new car and a few extra dollars a month are better than "I wish I had"
2011 GT/CS Convertible
GT Accessory & Security Package