I've just installed Doom and it runs consistently over 120 fps, which looks amazing on this monitor. I'm using Gsync, I haven't tried ULMB yet (someone recommended it here for high framerate games)
The benefits of QHD are more evident than ever here: enemies appearing far away retain all their details and the picture looks very, very sharp.
Having tried a X35 (an ultrawide with a VA panel), I loved the depth of the colours and I hated returning to my former TN monitor, where everything black looked grey. And I blamed the TN technology.
Well, it turns out that it was my former monitor which was really rubbish: the colours on the Dell look way better. One YouTube review was saying that it was hard to believe that it was a TN panel, that the colours made it look like an IPS panel, and I thought this was probably exaggerated. Well, I think the reviewer was right. I was apprehensive of Doom's dark colours, and I was wrong, it looks fantastic. Stunning monitor.