I gave this a try recently and I'm quite impressed with how well it works. Granted, I have what you can call a high-end system, but still I had expected a sudden crash either with the drivers, or the game or the folding core or all of the above. Neither happened. Game and system responsiveness did not suffer, but FPS was lower and folding performance degraded, both of which were very much expected.
 
To be specific, I used the 337.88 WHQL drivers with SLI disabled on a 2 x GTX 780Ti system. The folding priority setting was at "Medium". Both cards were folding and the game was processed by only one card.
 
It may be obvious for some and not for others, but if you intend to do this (gaming while folding) with SLI enabled, all involved cards' folding performance will go down substantially. In my limited experience with limited number of games and WU's, TPF increased as much as doubling. You might say it makes sense since the GPU was being taxed by two demanding processes fighting for the same resource.
 
In my experience, this is better than pausing the folding core while gaming. It's seamless; you shut down the game and folding core keeps chugging. Granted, I don't play games often, and a single GTX 780Ti is more than capable of handling the games I play...
 
I'm curious what others' experiences are in this regard. Or, have you not tried it at all?
 

I don't think it would work on the GPU, Maybe if you used only half your Cores and Fold only on SMP.
To Really Fold you need to run on Full and any other setting for Folding would not be worth the time or effort to complete any Projects. Most likely miss the dead line.
 
Added:
Maybe if you ran the game at 800x600 it might work.

If I'm folding gaming doesn't work properly so I always game with folding disabled. 

back when I used to do this some WU would allow this to work, other would not and would crash either the game or the whole machine.

Maybe I wasn't clear enough but I was talking about purely GPU folding. I don't fold on my CPU since it causes too much heat and significant drops in both system responsiveness and GPU folding performance (even with SMP 6 and Process Lasso).
 
So, yeah, my report was on just GPU folding and how it interacts with gaming...

i also have a single 780ti and i can fold while gaming on most games, not the newest high end games though.

Huh, interesting timing on spotting your thread, someone in another forum mentioned they didn't notice issues gaming+folding on a 750 Ti.
 
I used to game while Folding on the GPU, but that was back in the day when F@H utilized only ~60% of my GPU's performance leaving plenty leftover for gaming. These days using even a GPU-accelerated browser is a royal pain if the GPU is folding, and I can forget about watching video let alone actually gaming with folding going. I wonder if the 700's are different or if it's just because they aren't being maxed out yet... does GPU-Z report the 780 at 100% load while folding?

I should note that my GPU is a 780 Classy Hydro with a slight OC @ 1201mhz with mem @ stock.   Running a 3 screen desktop.  Don't game much in surround much anymore.  I only game on the middle 1080p screen and have the sides with online TV on one and browser/folding on the other.  I only play small games or wow during folding.  When I am on the forums daily helping people with water cooling, I turn on the folding and sometimes have the TV on the other screen going.  I can't have TV, Folding and gaming.  Don't think my i7-950 likes it too much. lol  I used to have one of my GTX 480s with my 780 and wanted to setup the 480 as a folder and 780 as a gamer but didn't want to ruin the software and my folding jobs/points etc.  It worth noting, the 480 is only around 30-40PPD, if I recall correctly which isn't worth the power usage it needs.  I had my second PC working for a few months till it stopped working.  Me thinks the MB isn't doing well.  Had the 2 480s on it folding for like 3 months straight producing around 70-80PPD total but the power usage was up there. lol  Have to figure out whats wrong with it before warranties start expiring.

Zagen30
Since you can't SLI a 480 and a 780, there should be no real impediments to folding on one while gaming on the other.  The only tricky thing is that FAHClient's indexing of the two GPUs might get a bit screwy, i.e. it might label your 480 as the 780 and vice versa.  A clean reinstallation after putting in the second card may help in that regard.

That's funny because I think that was exactly happening when I was folding on both 480 and 780.  The PPD would switch on each other and the 480 all of a sudden was doing 160k+ PPD. LOL!