DarkNecridIf you have a recent GTX card, it will already support this from a driver update, so there won't be a reason to update beyond keeping up with next gen games.
You need to have specific monitors. The first one coming out is a 400$ 144 Hz maximum ASUS VG248QE. (also the monitor won't work unless you're using an nvidia GPU that supports G-Sync, but this isn't 100% confirmed yet I think)
It benefits people on both sides of the FPS spectrum. If you get bad FPS it will make the refresh rate match it so it will look smoother (30 FPS on a 30 Hz refresh rate looks better than 30 FPS on a 60 Hz refresh rate), if you get great FPS (higher than 144 in this case) you won't get screen tearing cause of what G-Sync does and won't need to enable awful V-Sync.
Yeah, I'm using a fairly old AMD card at the moment.
Snagged my vg248 on eBay for $240 with free shipping, by the way :)