I'm testing Plasma Active 3 on Nexus 7, and there are various issues with usability. I'll collect these here:

1. No screen rotation.
This is a noticeable disadvantage - using books reader for example is much more pleasant in portrait mode. So far the only way is landscape. xrandr can rotate the screen manually, but it doesn't affect system touch coordinates, and all screen navigation is getting messed up up in such case. No rotation a minor issue though comparing to constant Reader crashing on zooming, but that seems to be a known bug: https://bugs.kde.org/show_bug.cgi?id=308240

2. No obvious way to change activity background to custom image.
When I open activity settings window (Edit Activity) it presents me with a list of predefined images. I see no way to select something different, which I for example just copied to my $HOME/Pictures or some other location. Is custom file selection missing there? So far I had to copy needed files somewhere to a subdirectory of /usr/share/wallpapers

3. Transferring data using "Files" manager is confusing or impossible
I couldn't figure out how to copy or move files using the "Files" manager. There is no context menu for files (I expected something like long tap on the screen, but that didn't help). Using dolphin for that purpose isn't much better, since it not created for touch screen, and expects right clicks. Am I missing something, or it's not implemented at all? The only method for moving around and copying files seems to be the terminal.

4. No touch optimization in Konsole.
May be it's just exact replica of desktop Konsole, but it's not really well optimized for touch screen. I couldn't figure out how to copy and paste text in it for example. While as mentioned above it's the only way to move/copy files around on the device (I usually end up doing it from another computer connecting to the tablet with ssh).