As far as I've understood, G-sync syncs the FPS for what's best for your GPU. Which usually is 90 for the high end gpus.
Wouldn't it then be impossible to utilize the 144 Hz on a G-sync monitor?
It would be possible many games you can run at 144+ fps(i run League of legends at about 300 fps) also there are people that run 4 780 Tis that have too much money on their hands. and even if you run it at 30 fps gsync will do wonders for you it completely eliminates tearing(this is what it was made for). What it does is makes the monitor work exactly in sync with the fps of the video card so if you get 47fps monitor will work at that moment at 47hz and you will have a perfect image with no tearing. ALso something of note is that non gsync monitor lets say running at 120hz and you have 60 fps it wont really look any different than on a 60hz monitor it just displays the frame twice(it is more complex than this but it would take a long time for me to type everything out you can google it).