Hello,
 
Right now I have an Acer H243H that has served me well over the years, but I am curious about 120Hz gaming and how my system will benefit.  I like to have eye candy on, typically as maxed out as I can go while maintaining consistent frames (goal of 60fps @ 60Hz).  I like to use Vsync because I hate tearing, and I have never experienced any negative effects (as long as I can maintain 60fps). 
 
It is my understanding that using a 120Hz monitor will allow my system to surpass 60fps without screen tearing, as long as my frame rate doesnt go passed 120fps.  Is that correct?  I would sort of "unlock" the power of my system, granted it could handle higher frame rates with eye candy on.
 
Here is a short rundown of my hardware which I do not wish to upgrade, since I would rather build a new system that takes advantage of PCIE 3.0, USB 3.0, etc.. (instead of GTX780s in my X58 mobo).
 
EVGA e760 Classified
i7 920 D0 @ 3.6Ghz
12GB Crucial Tactical Tracers @ 1700Mhz
2x GTX580s Black Ops Editions
 
Do you think I am capable of a good 120Hz experience?  I like to play BF3, COD series, and probably BF4 when the price drops.  I get 60fps solid with everything max in BF3.

When 27 or 28 inch 120-144 hz monitors are released with Gsinc, I'm getting 3.

I've had my asus vg236 3d vision monitor for a few years now and testing out 60Hz v 120Hz on this monitor i can tell a massive difference with 120Hz enabled even when normal 2d gaming, there is much less tearing with 120Hz, borderlands 2 at 60Hz is more than playable and framerate is way high of course but oh man i just can not stand the tearing and VSYNC enabled with triple buffering enabled does not really help and in fact vsync enabled- input lag is now ones enemy. For me personally anything over 60Hz on my monitor removes tearing, 120Hz is great but that does not mean my games do not stutter or in fact total tearing issues are gone, no, but what it does do is greatly smoothes out the negative effect of running my monitor at 60Hz or below (if i set my monitor to 60Hz some games detect 59.9, lol). I can't even stand moving my pointer over the desktop at 60Hz. 85Hz was always the sweet spot on my CRT monitors. I still think CRT monitors beat the lcd's, i miss the CRT days. It will be interestin to see what Nvidia can change with the G-Sync technology.

http://nvidianews.nvidia.com/Releases/NVIDIA-Introduces-G-SYNC-Technology-for-Gaming-Monitors-Tears-Stutters-Lag-Become-Artifacts-of-th-a41.aspx

Afterburner
My answer is going to not be technical, but rather seat of the pants...
 
I am running three ASUS 144Hz 24" monitors in Surround on a single 780 Classified running on an X79 DARK platform.
 
Gaming for me became "Fluid". The lag I was experiencing, or slow reaction times that I thought was a personal issue ended up being my monitor trying to keep up with me. 
 
I cannot express enough the pure enjoyment I experience now in Driving games and FPS games. That does not mean I am any better at gaming, just that the feeling of total fluid control is at my finger tips...
 
If at all possible, I shall not return to 60Hz...

Do you have this monitor? http://www.asus.com/Monitors_Projectors/VG248QE/ Edit: OK I see that it is the one you have.
This is the monitor Nvidia is selling a G-sync kit for http://www.anandtech.com/show/7436/nvidias-gsync-attempting-to-revolutionize-gaming-via-smoothness
It's tempting, but I'm wondering about the color of the tn panel. Aside from G-sync, I was wondering if this set up affects FPS. Another words, do these monitors raise fps so that your are able to eliminate SLI? Or, does it just smooth out game play enough to to make it playable at low FPS. I'm asking because I'm considering another Vcard as well. Thanks

I will put it this way. Since switching from 60 to 120 Hz monitor my eye strain is non existent. I prefer Samsung monitors. 

Quick question, has anyone used that asus 144HZ. Would that be better than the 120's.

Here is a good review on the Asus 144hz http://www.tomshardware.com/reviews/vg248qe-144hz-gaming-monitor,3609.html
I want to buy, but I would want to make sure I can get the G-sync kit for it first.

Thank you for all the suggested monitors and experiences with 120Hz vs 60Hz.
 
But what do you think about my system specs?  Would you recommend that I upgrade?  I just dont want to buy a 120Hz monitor and have my hardware struggle to perform.  I'm use to 60fps - no tearing.

ILikeBeans
Here is a good review on the Asus 144hz http://www.tomshardware.com/reviews/vg248qe-144hz-gaming-monitor,3609.html
I want to buy, but I would want to make sure I can get the G-sync kit for it first.

You can... Thread talking about it here...
 
http://forums.evga.com/tm.aspx?m=2052648

I have been reading about 120hz monitors and I am intrigued.  I would like to try one but I can't imagine going back to a TN panel after using my current monitor.  When I had an Asus TN panel the colors would shift just by moving my head slightly.  Also, I would see "rainbow" type colors on text sometimes.  
 
Is there an IPS panel than can produce true 120hz? 

Okay well, I pulled the trigger on this: http://www.newegg.com/Product/Product.aspx?Item=N82E16824014350&Tpk=24-014-350
 
Could not stop that price from looking amazing with the current BenQ additional 10%. 
 
At least if it makes my rig squeal I can return it.  For some reason I doubt I will do that though.  Didn't upgrade my size since I have 24'' monitor already, but the 27'' BenQ was over $100 more for a few more inches.  Meh.. I'll post how it is here when I get it next week.

The lag you get at 60fps depends on the game engine, some games are smooth at 60 while others need 100 - 120fps to be smooth.
 
recently I started to run my games without vsync, and I use MSI Afterburner to control my framerate cap and it works really well. The screen tearing is not that bad at high framerates, its only more noticeable at low framerates.
 
Setting a framerate cap is a good way to control the temp of the GPU as well, No point in the game running at 150 - 250fps, when you can set it down to 120fps or whatever you want and be smooth and the same time keeping the GPU temp lower.
 
I adjust the framerate cap based on the temp the GPU runs at or how smooth it feels, this varries game by game.
 
Until I can afford a 120hz monitor, this what I'm gonna do until then.

Afterburner
 
 However with the three ASUS VG248QE's (On sale right now for $240) ............

That price just seems to good to pass up.  Just ordered two to replace my current 24" Samsung SyncMaster 245BWs.
 
They've been nice for the 6-7 years I've had them, and till this day still don't have any dead pixels, but I've been curious to see what all the fuss about 120+Hz monitors for years.

Don't even worry if your rig can't hit 120 FPS in games. All the other benefits of that refresh rate are still there including the quicker mouse response in games and ability to use vsync without adding tons of mouse-lag. 
 
I can't peg 120 FPS in stuff like BF4, but you still notice the difference in refresh rate like night and day. 
 
Sometimes my NVCP likes to set my screen to 60Hz if I've been in the multiple monitors tab and I notice that immediately.