Thanks for all the replies so far. Interested to hear that the Gulfstream reputation for excellent customer service has slipped a little. To be honest that would have been the major reason for me to recommend them to my boss.
I suspect we will need a G6000 in the next 2 years, and maybe order a G7000 for 2018-19.
I've also had some PM's from pilots in Asia operating the G650 who tell me that it can't make the advertised range, as well as the (to be expected) "teething issues" of operating a new aircraft and a new type.