Several months ago the distribution I use decided to force plasma on everyone, and for me it made my desktop unusable. It was crashing all the time and doing other strange things. I was told to use the nvidia driver instead of nouveau but that made no difference whatsoever, so, quite annoyed, I went back to kde4 which was in some really strange state due to the way packages are handled (some things required kde5???)
Recently after trying to apply updates it was not possible to stay on kde4 unless you stopped updating. kde5 is now stable that I turned off all compositing and desktop effect crap. HOWEVER, task switching is so damn slow it constantly interrupts my workflow. You press alt+tab, and nothing happens. You press it again, nothing happens. You press it three times in a row, and FINALLY, it decides to scroll through open windows. It's frustrating as hell, and yes, I've tried changing task switcher properties, and none of the many settings I've tried fixes this.
I wish I just hadn't updated my PC, security fixes be damned.