So, I finally got a chance to unpack and try out the monitor, and things are looking promising so far. The box arrived in great shape, and I like the understated, professional look of the monitor a lot. You wouldn't be able to tell that it's a gaming monitor, except for the (removable) NVIDIA G-Sync sticker on the monitor stand's base.
Also, most importantly, there are no dead or stuck pixels on my screen. Panel uniformity seems decent for a TN, but there is the obvious TN gradient where the top and bottom have differing brightness. This is not really noticeable in-game, however. I've attached some images of the panel for gray/red/blue/green/black backgrounds so you can judge yourselves.
The AG coating is on the aggressive side, and I would say it's on-par with my LG 34UM95. On solid whties, you get a little of the AG sparkle. Here's a panel reflection shot to get an idea of the AG strength.
As far as using the monitor, G-Sync works great in 144 Hz. There was no problem connecting it and getting it up and running with my 980 Ti. I also tried out ULMB in 120 Hz (G-Sync disabled), and it also works fine, although it of course dims the screen significantly. It allows you to vary the pulse width of the ULMB mode as well, but I kept it at the default setting of 100.
There does seem to be a slight difference between 144 Hz G-Sync and 120 Hz ULMB modes, which is most visible to me when I move the Windows cursor against a dark background. In-game (CSGO), I can't really tell if there's much benefit, but I honestly haven't used either mode long enough to say for sure. Any difference in smoothness between 120 and 144 Hz isn't immediately noticeable to me.
The HDMI port also works perfectly, so anyone holding out on the PG278Q for an HDMI port will be happy. It recognizes my PS4 without any issues.
Overall, the monitor seems to be working really well thus far, and hopefully it's a sign that the QC problems with the PG278Q are not going to resurface with Dell.
The only issue I've encountered is not even with the monitor, but the 980 Ti, which seems to run at high clock speeds when the refresh rate is set to 144 Hz, even on the Windows desktop. When I reduce the refresh rate to 120 Hz, it goes back down to normal, idle clocks. For now, I've just left it at 120 Hz to avoid chewing up energy in desktop mode and boost it to 144 Hz before I'm about to game. If anyone has a solution to this, I'd love to hear it!