I have been using Ubuntu MATE more recently and I am loving it but I find myself wishing it had one feature which is present in the GNOME release of Ubuntu and serves to make the main Ubuntu release feel like a bit more of a cohesive and well-integrated "product".
I notice that in Ubuntu GNOME when the screen locks through inactivity, or the user locks it with Super+L, the system will also signal the display to enter poweroff/standby immedaitely. I think this is a good approach. In Ubuntu MATE, however, when the system is locked like this then the screen does turn black, but it does not turn off. The display will then stay turned on (just wasting power and displaying only black) until the timeout configured in the "Display" settings of the Power Management tool is reached.
In my case, this means that when I lock my desktop or laptop, the display will remain turned on displaying an empty black screen (but with backlight enabled and using power) for 30 minutes before it eventually turns off.
This is a concern from a power usage perspective if Ubuntu MATE is shooting for power efficiency, as I've heard Martin Wimpress note on the Ubuntu Podcast in the past as being a goal of the project. It's hard to describe but it does also have the effect, as I suggested before, of giving the distro the feeling of a lack of polish when compared to display standby-on-lock being the default behaviour for GNOME, macOS and Win10.
On a less important but related note, it seems like GNOME on a laptop will turn off the keyboard backlight in unison with turning off the display while on Ubuntu MATE the backlight just continues to persist when the device is locked, even once the display has finally powered off.
I don't want this to come across as entirely negative though, as I am a big fan of most of the other design decisions of the flavour. Thanks to all for the great work