Edit: My first unit had a patch of backlight bleed in the top left which was super noticeable, so I returned it. My second doesn't have any blb, but unfortunately it has 3 dead pixels in the lower left of the panel. Not sure if this is indicative of the current batch of these monitors, or if I just got unlucky. Will likely return this second unit as well, as for this price I really don't want to have any panel defects.This is a fantastic 4k high refresh monitor. It has a fairly subdued look other than the the LED lighting on the bottom and back of the monitor, which can be disabled if you choose. When enabled, I think that it provides a nice amount of bias lighting.This monitor offers very good sdr performance out of the box. By default, the wide color gamut is enabled. The monitor offers an effective sRGB emulation mode however, which is a welcome feature. Often panels with a wide color gamut don't have the ability to limit the gamut in typical sdr use like on the desktop, which results in over saturated colors. Having the sRGB mode eliminates this.With my i1 display pro colorimeter, I measured an average DeltaE of under 1.0, with a maximum of 2.3. Native color temperature is 6700k, which is what Acer actually calibrates these to at the factory. Native contrast ratio of my unit is 1065:1, which is typical for an IPS panel. Gamma was slightly off, as it was too high on the low end (making near dark tones too bright) and slightly too low at the high end (making brighter values too dark). Of course after full calibration using the colorimeter and DisplayCal, the performance is exceptional, with perfect gamma, deltaE values below 0.5, and 6500k color temp.The SDR variable backlight in the OSD is enabled by default. From my testing, it seems to enable a crude form of local dimming- only 3 or 4 zones. In practice it doesn't really do much of anything, I saw improvements to contrast ratio of only <50, which is barely noticeable. The good news is that you can't really notice it in practice. I think it's subjective whether you want to have this enabled or not.The HDR performance of this panel is actually pretty surprising. It's only certified hdr400, but the image quality is much better than other hdr400 level monitors I've used to this point. The color accuracy in HDR is excellent and is just as good as in SDR, and tone mapping is done quite well. I found that games with good HDR implementation look amazing on this monitor, with the weakness being that dark areas are really not that dark. Since this panel does not have full array local dimming, dark areas will never be very dark, but the way this panel tone maps HDR content makes the image appear much higher contrast than in SDR. Bright, outdoor scenes especially look amazing. Whether or not the extra $600 for full array local dimming on the X27 is worth it is debateable, as the local dimming does cause haloing around white objects on a dark scene. Suffice to say though, for most users the HDR performance provides a nice boost on games and videos. I've shown a few example pictures in this review.The fan is not very noticeable in my setup. The sound of my air cooler in my PC drowns it out. Just be aware though that this monitor does have a cooling fan that does ramp up when using HDR.Due to the gsync HDR chip, hdr and gsync can be used at the same time. For full 10 bit color, you will need to limit the refresh to 98hz. Since most games struggle to go above 98 fps at 4k even on a 2080 or 2080ti, this isn't a huge problem. You can also choose to run it at 120hz, which will limit you to 8 bit. In practice I couldn't tell a difference between the two. If you overclock to 144hz, it will enable chroma subsampling, so I don't recommend it.I'm using a 2080, and I can easily get 60+ fps in newer titles by just turning down a few settings. I tried games like division 2, BF V, AC Odyssey and Shadow of the Tomb Raider in 4k HDR and they were quite amazing, and I was able to get over 60 fps without too much trouble. Since it also has gsync, fluctuations in fps are smooth. Also, most newer games have resolution scaling and such that will allow you to adjust down and reach higher fps, which is beneficial in competitive games and such. In short, it's an excellent high refresh gaming monitor.I took one star away because of two issues my unit has. First, there is a bright spot of what appears to be backlight bleed at the top left of my panel. It's noticeable on a black screen or in dark scenes in games, enough that it's bothering me. The rest of the panel however is very good, and the IPS glow is on the lower end in comparison to other IPS panels I've used. The second issue is two dead pixels in the lower left of the monitor. Honestly, the pixels are so small that its in no way noticeable during normal use, and can only be scene when looking for it (i.e. in a dead pixel test screen).For a $1200 monitor however, these two issues are enough for me to want to try an exchange. Overall though, this is a fantastic panel packed full of gaming features. At about $600 less than the X27, I think this monitor offers better value for the money, even though it's still very expensive. HDR content is still limited really, and these 4k high refresh panels are still limited by display port 1.4, so HDR is still not fully mature on monitors. I think this panel does HDR "good enough" for current standards. It will not match a good 4k HDR TV, but you also won't find a TV with 4k high refresh and gsync.