I fly the 5. No other way to say it, it does anything you ask of it. Short fields, long flights no problem. 3 words sum it up, performance, performance, performance. At full gross weight takeoff it's guaranteed to be able reach an initial cruise altitude of FL410 (about 30 minutes). The price? Three words, fuel, fuel, fuel.
The fabled Gulfstream support is just that, a fable. Maybe if your airplane is under warranty you can get the service everyone raves about. 10+ year old airplane? Forget it.
Gulfstream does give operators tons of info and resources for pilots I have not seen offered by other manufacturers before.