It's one of those epic questions, Vsync on, or Vsync off.

Vsync on:
-Perfectly aligned frames, no tearing.
-Less likely to crash.
-Locked at you're monitor's refresh rate. Usually can only go to 60 FPS (mine goes to 75 FPS though... somehow)
-FPS can bog down more then vsync off.

Vsync off:
-Virturally unlimited FPS....
-More likely to crash, but the difference is generally pretty low. (It depends on the card and the game)
-FPS does not bog down.

I'm actually interested to see what the results are. I personally keep vsync on, as I like the frames to be smooth as silk. As far as I know the human eye can't see more then 40FPS, but I'm posting this to see other people's point of view. Maybe there's something I'm missing.

I leave it off. It really serves no purpose. When frame rate is low enough that you see tearing with vsync off, turning it on will further drop frame rate, which makes no sense. When frame is high, you won't see tearing anyway, so there's no point in restricting frame rate.

 
 
You are missing the fact that what you ask is a fallacy based on a false dilemma
 
Let your immediate needs determine if you need V-sync on or off, based on the advantages and disadvantages.
 
It takes mere seconds and zero effort to turn V sync on or off and judge the results accordingly.
 

as far as i know the eye can notice the difference between 0 and about 120fps (i know i can tell the difference between 60 fps and 85fps). This is an interesting read... http://www.100fps.com/how_many_fra [...] ns_see.htm
 
my personal favorite is vsync on because of all of the positives that have been stated in the top post + i think 60 fps is alot more playable than tearing. Infact i consider tearing to be barely playable it is that horrible to look at
 

maybe your monitors refresh rate is 75Hz i used to run @ 85Hz on me old crt therefore i had 85fps.
 

bollix.
 
EDIT: I think this is an interesting topic and can't wait to see the end results for the poll.

That's why I stated "maybe there's something I'm missing". When I turn Vsync off on CSS, it looks like crap. There is horozontal tearing everywhere. When I turn it back on, it looks fine. Sure the frame rate goes up to 120 on occasion, but the 75 FPS that I normally get instead is fine... I can't tell the difference. Like some people have said here, they can't see the tearing, but I can. In other games I can see the tearing too.

In my drivers, its set for application managed.  Can't say I've ever messed with it one way or another.  

Vsync brings noticeable improvements for me on COD4 at hi res, but I go back and forth.

I had a game that would tear horribly if V-Sync was off, so I turned it on.  I was lazy, so it never got turned off, so my vote is for on.

 
Yeah my old CRT did too. I was just assuming that everyone had LCD's these days

Not everyone.  I can't stand the buggers, CRT until my flaming eyeballs fall out.

But if the monitor can only refresh 60 times per second (or  75 or 85) does it actually make a difference that your video card is outputting 120fps? I'm missing something here.

No you're not.  You are absolutely right.  Sort of blows a big hole in the "I can see the difference between 100FPS and 120FPS" argument.  You can really only say that if your monitor can output at 120Hz, which few can.

 
yeah thats a good point. the only reason i could notice the diff between 60 and 85 was because my monitors max refresh rate was 85.

Yeah I have an LCD monitor with a refresh rate of only 60hz. I'm no videophile, though, so anything above 30fps looks good enough for me.
 
On-topic, though, I have never had any problems with tearing so I completely ignore Vsync unless I want to see exactly how much more I can turn up the graphics settings or do some kind of benchmark.

That's what I always thought.... then why do people turn of Vsync if it doesn't really change anything, except horizontal tearing... which makes it look worse?

most games on....source games do not like it sometimes(seems to make lag spots near fire oddly enough) so its off there

and to some above...high fps DO show the page tear effect..

i use vsync in every game i play.  The tearing looks awful sometimes...

The arguments on here about your monitor only being capable of 60 fps anyway are right on.  And anyway, whether or not the eye can tell the difference between 50 and 60 frames per second, I'd choose 50 any day if it meant the image wasn't literally being torn to hell.

Depends on the game I suppose. I recall turning v-sync off in a space sim and the graphics became distorted. Switched it back on and the graphics were fine again.

 
Exactly my thoughts on the matter.