Bought myself the Asus PB287Q (Catchy name I know). With DisplayPort it is capable of running 4K res at 60Hz. It's a little sparse on inputs compared to my old Monitor, features 1 x DisplayPort, 2 x HDMI, 1 audio jack.
It's glorious! Apologies for the bad photos. My phone isn't the best indoors.
Now to the good stuff.
Here is how big my browser window is, this used to almost be fullscreen on my old 1440p monitor. With some room down the side for Skype.
Here is a 1920x800 Blu-Ray movie playing at native res
It has this "Picture in Picture" mode. Where it displays 2 sources at the same time. Although I won't be using it. Here it is with my PS4 on the top right.
The alternate mode is "Picture by picture" where they get equal space.