I switched to UM (18.04) a few days ago after spending a lot of time with other Ubuntu flavours, and sometimes other distros. (For completeness' sake I should probably mention that I dual boot with Windows, though I generally only use it for things that are either impossible or too much of a headache under Linux.)
Great! Everything works just as it should, and some of the artwork and visual design is my favourite in Ubuntu so far. And I haven't run into any serious bugs or other problems yet. Thank you for all the great work!
It would be nice if you could set separate times for the screensaver and the automatic screen lock, so that, for instance, your screensaver would turn on after ten minutes of inactivity and the screen would lock after 30 minutes or something like that.
It would also be nice if the slideshow setting of the screensaver could be set to get images from a different folder than the main images folder.
It would be nice if there was some way to export all your desktop settings into a file, so that you could easily import them on a later installation or a different machine.
And one thing that's more about Ubuntu in general: it would be nice if, somewhere in the repositories, there would be a countdown timer package that would allow you to run several countdowns at the same time. All the countdown timers I could find only allow for one countdown at once. If you're cooking several things at once, several countdowns can be very useful.