I was randomly browsing a Saturn Sky Forum and one member had both a 'stang and a Sky redline . . . he was selling the Mustang. That made me really sad (despite how cool the solskies are).
My prioritized list of new cars to buy goes as follows:
1 - Mustang GT
2 - Solstice
3 - Corvette
4 - R8
5 - Pontiac G8 GT just to add some 4 door sensibility to the mix
While I might not actually get to buy any of those new, I'll definitely be all over the used market in the coming years.
Anyway, you'd be getting rid of my favorite new car for my second favorite new car, hehe

. The only advice I have is to consider some of the more noticable pros and cons. Fuel mileage and lack of bulk side with the Solstice, but the Mustang does have more usable cargo space and seating . . . and a V8. Overall, t depends on how you generally use the vehicle. Ok, I'm going to stop being captain obvious now. Good luck . . . you should atleast get some good test driving in for us, perhaps with some other options as well.