The 4K monitors at 27" are just too small for me. Unless the monitor is right up in my face I can't read the text. So then I have to increase the display size. And then I'm right back where I was....no net real estate increase. At 27" I am happy with 1920 or 2560. For 4K (reading at 4K), I think you need to be more into the 32-36" size. And then you're only using 1 monitor.
DPI/PPI is still a big concern to me.
You are right, it doesn't work for everyone. I am one of those weirdo's that uses a 4K 15" display at 140% scaling. Most people use 250% for that. But my vision is perfect and I can still read text on my screen from a few feet away.
I just saw the Dell 25" 1440P displays at a great price (only 50€ more than a 24" 1080p Ultrasharp). I might buy those as they seem great price/performance and PPI. Just asked our guys and they think 2x 27" is way to big to be comfortable. In my eyes a display cannot be big enough (if you have room to place them a bit further), but they have to use it, not me.
These are the systems:
4x MSI X99A SLI PLUS
4x Intel i7 5820K
4x G-Skill 32GB DDR4 2400 CL15 black kit
3x Seasonic G650 (indien we dit bij Alternate bestellen)
3x Fractal Design Define R4
3x Cooler Master Hyper 212 EVO
1x Samsung 850 EVO 500GB
1X Nvidia GTX 750 TI Gigabyte
Ordering parts tomorrow.
Also found a deal on 6 month old Herman Miller Aeron's. Instantly went there to get them
I got 8 of them, but only 6 in pic: