I have a G8 GXP that I bought back in August and so far I am loving it. It handles well and goes like a raped ape! I don't drive it everyday and have only put 4k miles on it but have had zero problems so far. My only complaints are trivial stuff like the wobbly glove box door and the cheap feel of the parking brake handle. Also, I went with the manual trans and would probably pick the auto if I could do it over again just 'cause I'm lazy and it's not a great trans to teach my kids to drive on.
I'm 6'6'' tall and go about 225 lbs and am usually only comfortable in a p/u truck, but this car has a ton of leg and headroom. My two teenage boys (both over 6') and I drove to SLC, Utah in Sept and we were comfortable on the long haul.
If you can get a GT for a decent price I would go for it, it's a great car with lots of power and a nice sleeper appearance, you can slap a rotofab CAI and a tune on it for cheap and blow the doors of of most everything else on the road.