The few games I've tested at the 12.5 resolution did show respectable average FPS:
 
Built-in Game benchmarks tested (with VSYNC @60 FPS):

• Sniper Elite 2: max settings except super sampling off. Average FPS 55.65
• Tomb Raider: max settings with TresFX except FXAA for AA. Average FPS 56.2
• Metro 2033: High, MSAA 4x, AF 16x, PhysX:Yes, Tessellation:Yes, DOF:NO. Average FPS 57.23

However for me the experience was not better than my "regular" 3-monitor surround (horizontal) at 6016x1200. Things that got in the way:
- Too many bezels! Perhaps it's just me, but when stacking monitors vertically the bezels really distract me. Feeling "behind the bars" :) And stacking 5 screens horizontally does not really make sense, the image distortion on the edges would be too much.
- Game textures don't really shine at those resolutions -- objects seem a little "overly zoomed". Perhaps with exception of Lara Croft's face :) Perhaps it would look better on smaller pixel size screens than my 24 inch ones.
- Smoothness is gone for the most part. With 3 overclocked Titans I am spoiled by seldom seeing my games dipping below 60fps. I use v-sync at 60fps, and most of my games fully maxed run very smoothly at the "regular" 7.2M pixels resolution at constant 60fps. At 12.5M pixels I saw choppiness, perhaps less pronounced in Tomb Raider. Metro was very choppy. I did apply the Nvidia x79 PCIe 3.0 fix and had the cards running at 16/8/8 3.0 speed (my 4th slot is occupied with a sound card hence only 1st card runs at 16x speed)
- Some quality settings trade-offs. I had to lower the settings below my usual, for example moving to FXAA from MSAAx2 in Tomb Raider, and disabling Super Sampling in Sniper Elite 2 from the usual 2.25. On large (1920 tall) screen it shows, at least to a "trained eye".
 
With all the above, I will keep my 3-screen setup for now (at least as long as I keep Titans). Nevertheless I am very happy NVIDIA continues evolving its Surround support! Perhaps by Maxwell-2 or Pascal there would be some truly bezel-less monitors to stack vertically. Or someone would release a "4-5K" 21:9, 50-60" diagonal, 120Hz curved screen for immersive gaming :)
 
Some screenshots:
 







 

Yes, something like that plus 120Hz/1ms :)