Well I've had mine for a few days now and I've mixed feelings if I'm honest.
On the plus side it seems well built, no dead pixels and is defiantly noticeably smoother @ 165Hz vs 60Hz of my two old Dell U2312.
Backlight bleed is a bit meh. It's hard to capture on camera, and it is noticeable, but around the same or perhaps only slightly more so than the U2312 depending on your viewing angle.
I suspect it is about average for this type of panel so I don't think it is worth trying to exchange it for a better one.
As noted the monitor does disconnect from the DP when you power it off, with no option to adjust Deep Sleep Settings, but it doesn't appear to do it in standby.
This doesn't really affect me as I rarely turn them off but it isn't an issue with the U2312.
The dim second row of pixels @ 60Hz is also present, although quite hard to notice and again not an issue for me running at higher refresh rates.
I haven't had any issues with any screen blanking on a triple monitor setup, with the others monitors running a different resolution and refresh rate (3x Display Port from a 2070 Super).
Out of the box calibration was very close - I ran it through an Xrite i1Display and there was only a marginal improvement. I have had to turn the brightness down from the recommended settings as I found it too much for my eyes.
I was initially disappointed with the amount of "glare" around icons on a black desktop, and text was very difficult to read - However a cleartype font calibration helped with that and either my eyes had adjusted or the monitor has settled down and seems a lot better now.
Overall not a bad monitor but coming from a 8 year old 23" IPS panel I wasn't exactly blown away with the improvement, and in some cases a few features felt almost a retrograde step.
I think that is more of a comment on the current state of monitors in general rather than the S2721DGF specifically. I think Dell have done a decent enough job with this panel, but the panel itself could be better.
I suppose I was hoping for a lot more from a decade of technological advancement in this sector. If anything it has made me appreciate how good my U2312's were, especially as I got two for the same price!
I'm still within my 14 days and giving it a good test, but I suspect I will keep it.