I can add some info here.
I've currently extensively tested the Acer XB252Q versus a (almost flawless) Samsung CFG73 (VA) and my previous LG 24GM79.
The Acer Predator XB252Q has horrible settings from the factory. You will need to calibrate. But here are a few points from my own experience and a little something to think about in regards to its competitors. Keep in mind I do not use any tech for measurement, I use calibration tests and personal experience only. Also keep in mind this is in regard to the panels I personally own or have owned, and your experience may vary (due to panel lottery):
+ Very good colors after calibration. It's no QLED panel when it comes to gamma-shift and color depth or viewing angles, but it's superior to the LG or Acer Predator XB241H, especially due to having minimal clouding and minimal backlight bleed even with brightness settings up high. This 25'' panel seems to perform better than the old 24.5'' panels in general. This goes for the Asus and Alienware models as well (the Alienware is an even newer version of this same 25'' panel). However this only goes for the *GSYNC* models. The freesync models are a lot less consistent from what I've read from owners who own both versions
+ Great pixel responsiveness. The fastest I've seen actually.
+ The Gsync module on these panels allows Gsync all the way up to 240hz and this does not add any input-lag compared to a normal framerate cap. For instance: CSGO/OW/Fortnite with Gsync on a 238FPS cap adds 0 extra input lag, which is amazing and gives an even smoother and micro-stutter/tear free image. According to the test I'll post at the end of this message and several tests on blurbusters.com it's only worth toggling off gsync for less input-lag if you can reach over twice the monitor's refresh rate in terms of frames per second. So unless you can hit 500+ fps in CSGO, for instance, it's probably more beneficial to play with 238fps cap & gsync enabled. Yes, I know that sounds crazy.
+ ULMB implementation, motion blur reduction, is slightly above average at 144hz (the max you can use it at) on all panels and can still be up to 300cd/2 in brightness, which is impressive. There is almost no contrast lost compared to the ULMB 120hz implementation on the 144hz gaming panels.
-The Asus and this Acer will
have overshoot artifacts even with Overdrive on 'Normal' when set at 240hz. This is not there on 144hz mode. You won't notice this in-game, or even the Blurbusters UFO tests, however you can provoke this by dragging for instance this forum window around. You will see slight white-trailing behind text. Setting it to Fast or Extreme will exaggerate this issue greatly. From what I've heard: Overdrive is calibrated the best on the Alienware AW2518H (not the Hf version!). The downside of that monitor is that it uses BT.1866 gamma and doesn't give you any gamma-options in the OSD if your unit is badly calibrated. I've not heard many reports on that though.
All in all this is a great panel, but I'm also curious to try the newer Alienware AW2518H myself, due to the claimed better overdrive settings. I'm very, very nitpicky however and I've not heard many people complain about the Asus PG258Q or Acer Predator XB252Q overdrive settings, so apparently many people don't notice it at all.
The things I like best on this panel are the extremely good (competitive, even) gsync implementation (even Gsync with a 144fps cap will make it feel, visually, like 180+hz due to how smooth it is), its good colors and ULMB implementation without any annoying backlight bleed. It has a very, very small spot of BLB in the middle-centre of the bottom screen, near the bezel, but that's it.
Here are some in-depth tests on Gsync on the 240hz panels (all use variations of the same one!) that show there's no additional input lag even in competitive gaming: https://www.youtube.com/watch?v=F8bFWk61KWA&t=969s