1) I have 36k miles and few problems this far.
2) My hood paint chips when the wind hits it. Drives me crazy b/c I really drive like a granny. No tailgating, etc.. Driving me insane... Make sure the intermediate shaft (steering) has been repaired. The fog lights...just rip them off the car. There are several posts about how F8cking unreliable they are. I had both housings changed and my bulbs last about 10 months or so and they are NOT simple to change. I have an LED bulb blown in my radio...there are no more replacements for many of the interior parts since the GXP has black faced instruments and other Bonnies have gray.
3)Yes, yes, and yes. Wish I had the money to buy the extended warranty. Didn't have 2k to plunk down.
4) Not great. I can get 25 highway if I cruise easy ( I once got 29mpg in Michigan over two tanks of gas, but that'* just cuz Michigan rocks
). 18-19 city and that is with premium. Prem. is not required but mileage on regular sucks.
5) Very few. I can't even find a molded plastic rock deflector for the hood.
We mainly use ours as a long trip car. It is not a good daily, in-town driver IMHO. The fuel consumption for town driving is atrocious (thus my Nissan). On long trips it is the best. Uber-comfortable and powerful. The dash kicks a$$ and the sound system is great. I wish they had put the "corvette" seats in the GXP like are in my SSE. There is simply no seat more comfortable than those (although I like the look of the GXP seats better - they are cleaner looking).
The drive train is worth all the quirks.
Even with these relatively minor problems, the lok of the car is AWESOME. It is a very unique car and no one knows what it is on first sight. The 18 inch wheels paired with the wedge shape makes it a great look. And then there is the exhaust. Heavenly noise, really.
I would buy a second one if the wifey wasn't hung up on getting a minivan .