The 4k resolution and scaling can cause issues with some apps as you noted. This is especially true if you use multiple panels with heterogeneous resolutions, connect with displayport and occasionally turn one monitor off. This causes windows to move everything to the other display which is a mess. However after futzing with it for a few days post-purchase I had it all working well enough to deal with, even though I occasionally get slack in an over-maxed window on the smaller display. Btw this program is really useful for smoothing mouse movement between the larger and smaller displays in windows 10: https://github.com/mgth/LittleBigMouse
At 4k 150% scaling you end up with the same screen space as 2560x1440.
[0] http://www.dell.com/en-us/work/shop/dell-43-ultra-hd-4k-mult...
They've released the UP2718Q at a serious price difference. I'd like to see one in person, but a 3x price increase requires a lot of improvement over an already great monitor.