Well, I've only owned my G751JT (without G-Sync) for just under a month now and can assure you that it's an absolutely brilliant machine. Well worth every penny, really fast and very capable of playing the latest games at high settings. The jury is still out on whether G-Sync makes enough of a difference to quality the higher price tag though, when it's possible to push the screen refresh rate of the non-G-Sync model up as high as 100Hz.
Asus ROG G751JT-T7115H
17.3" IPS, Intel i7-4720HQ, 16Gb RAM, NVidia GeForce GTX970m, 256Gb M.2 SSD + 1Tb SSHD