I just got and set up my Dell 24-inch IPS 4K monitor. I connected this monitor to my Surface Pro 4 with the included Mini DisplayPort to DisplayPort cable. This monitor displays at 3840x2160 at 60Hz. I now have 2 screens. The Surface Pro 4 2736x1824 screen and the Dell p2415q 3840x2160 screen. I also now can connect 4 USB 3.0 devices up from 1 USB 3.0 device thanks to the USB 3.0 hub ports in the monitor.
You can find all about my 4K monitor here.
You can find all about my 4K monitor here.