- There is a noticeable (to me) brightness shift with viewing angle changes. When the monitor is on the back of my desk and displaying a flat color across the monitor, I see a noticeable gradient instead of a flat color because of different viewing angles between looking head at the center pixels vs being off axis to the side pixels.

- The adaptive brightness backlighting doesn't do a very good job. Full bright white pixels in a dark areas will be noticeable dark compared to full bright white pixels surrounded by other brighter pixels.

- If you have some bright pixels in an otherwise dark area, the backlight cell built into the monitor there noticeable brightens, putting an approximately once inch by one in halo around the bright pixels. For example, this halo shows up around the mouse cursor when moving across a black area.

- I tend to work with light text on a dark background. The monitor makes the darks too bright (from the backlight bleeding through) and the brights too dark (because the backlight around there isn't on all the way). Everything is muted. It's noticeably less contrasty, colorful and alive when used with light on light than two iMac 27"s I have had.

- Although the PPI specs are the same, there's something about the pixels on the XDR that makes them more visible and less smooth to me than on the 27.