One other thing I've noticed that seems to be exclusive with IPS panels, although I could be wrong, I've only seen this effect on IPS personally. Its the rounded edge effect. If you aren't far enough away from the screen the outside edges of the screen seem to curve back into the display, almost like a curved screen phone. The effect goes away as you back away from the screen, but if you sit too close you will lose a bit of the outside edges.
I was about to purchase the Acer 3440x1440 X34 monitor, but I was checking it out at my local MicroCenter, and the effect really bothered me, and it was right at the range that I would be sitting from the monitor. I ended up going with a VA panel display instead. It doesn't look as good as the IPS panel, but that roll off effect at the edge would have driven me crazy.
If you have a local store that carries the display you are looking for, go check it out in person. There may be something that you didn't even think about that's a deal breaker for you. Also if you buy it locally, you will have a much easier time returning/replacing it if it does have problems out of the box.