Thinking about it a little more, while this reduces lag, you can't eliminate it like nvidia claims and here's why.
At the moment, whether vsync is on or off, once the GPU has rendered the frame, it doesn't get displayed until the next monitor refresh (this is independent of the refresh frequency, of course) so you get lag. The amount of lag will vary too, depending when in that cycle the GPU has rendered the frame. If vsync is off, then you'll get tearing and stutters, regardless of whether the GPU is rendering faster or slower than the refresh rate. Remember there's still lag in the system due to the rendering time of the GPU and general propagation delay through the controller and also the rest of the computer.
Now you turn G-Sync on, what happens? The monitor waits for the GPU, not refreshing until it gets the command from to do so. This results in the frame being displayed the instant it's ready. Lag may be reduced, but not eliminated. Tearing and stuttering will be eliminated, however, because the monitor will be displaying every frame and crucially only ever doing so
once.
Lag isn't eliminated, because the GPU still requires time to build the frame. Imagine an extreme case where the GPU is slowed down to around 15-20fps (can easily happen). You'll still have lag corresponding to this variable frame rate and therefore the game will feel horribly laggy. Responsiveness to your controls will be improved however since the monitor displays the frame as soon as it's ready, but more importantly perhaps there will be no tearing or stutters, which is a significant benefit, because both of these effects look bloody awful. NVIDIA obviously gets this.
The only thing I wonder is if the player will notice dynamic artifacts with the game responsiveness, since the frame rate and synced refresh rate vary continuously and significantly? It might lead to some weird effect where the player feels disoriented perhaps? Maybe even inducing nausea in some people? I don't know, but this is something to look out for and I will when I get my hands on some demo hardware. NVIDIA are obviously not gonna tell you about this in a press release, lol.
So, in short, while I can see this technology improving the game play experience, there's still no substitute for putting out frames as fast as possible. I'm currently gaming at 120Hz with very few dropped frames which makes a world of difference over 60Hz. (Adding LightBoost strobing to the mix with its blur elimination then takes this experience to another level altogether). That doesn't change with G-Sync. It would be really interesting to get my hands on demo hardware and see G-Sync for myself.
Well quite clearly, you're the one playing dumb, seeing how you have yet to explain to me why someone running a 120Hz or even a 75Hz monitor, would benefit from DROPPING the refresh rate to the frame rate of the game. Can you point out to me, a single person suffering from their monitor's higher refresh rate in any games that never even exceed it? It has never been a problem and Nvidia are yet again trying to fix a problem that never even existed in the first place, and quite clearly you are being ignorant by ignoring simple facts and have not had any experience with what causes tearing.
If a monitor is running at a refresh rate above the framerate of the GPU, unless the monitor does some image post-processing, scaling or duplicates frames (like those 240Hz TVs), the monitor will only draw the frames it has. End of. That renders this G-SYNC gimmick worthless because it is trying to show a problem that was never there in the first place. Whether your monitor runs at 30Hz or 120Hz it will only draw the frames that it has -- if it is less than the refresh rate, it won't affect the monitor either way.
I don't think you properly understand what G-Sync does on a technical level or what causes tearing and stutters in the first place. Remember, the only way* to remove stutters is to have the GPU and monitor synced, it doesn't matter which way round that sync goes. NVIDIA have simply synced the monitor with the GPU ie synced the opposite way round to how it's done now.
Check out my explanation above and in my previous post a few posts back. Getting rid of stutters and tearing is a big deal, possibly even more so than the slight lag reduction. This feature may be proprietary for now, but it's no gimmick.
*Not strictly true, sort of. If I run an old game which is rendering at several hundred fps and leave vsync off, then it looks perfectly smooth, with very little judder or tearing - and noticeably less lag. It seems that brute forcing the problem with a large excess number of frames per second rendered by the GPU can really help, even though those frames are variable.
. What you dont get is i want microsoft free gaming = No direct X fyi