I've had my Dell 2715q for a while now and I thought I'd share with everyone how they are. I find them to be fantastic for photo editing and at $600 bucks a piece, they are almost a must buy.
First, editing in 4k is a revelation. Many of my cameras are still 12mp-16mp, and the images are almost 1:1 on my screen. I'd never go back to older monitors once I got used to these.
The monitors themselves are well built, plastic but quality plastic. The screen has about 5 USB ports so they are very useful (although I do miss the built in SD card slot on older dell monitors).
The monitors cover a 100% of sRGB and can be calibrated with affordable third party devices such as spider pro.
Now here is the trick, to make TWO 4k screen work, you will need a fairly new graphic card. I use R9 x290 from Radeon. The card needs to support 4k and have one Display port 1.2 AND at least a HDMI 1.4 port for the monitors to work. Here is why:
If you plug your first monitor in the Display port, and daisy chain the second display into the first one, you will have two functional screens, BUT at 30HTZ refresh rate which is not smooth. You will need to connect one display to the display port, at 60HZ, and the second display directly into the second port on the graphics card (my card doesn't have two display ports), at 30hz.
If you want 60hz on both screens then you need either a SLI or cross fire (two graphic card set up), or a cutting edge new card, which would cost a lot of money.
For me, one screen at 60hz and one at 30hz is fine since I use the second monitor only for proofing images at full screen.
hope this helps