A lot of people report that Plasma 5 does not work for them or breaks after some time. There is one bug that you should know about. As mentioned in this post https://goo.gl/Yb1lHz sudo not always is your friend. +David Edmundson explains it:

When you run something with sudo, on some setups that transfers $HOME, the variable saying where your home directory is.

This causes some graphical apps to write some things as root in your home folder, in particular inside .cache.

When the next app comes along, it can't open a file and has an emotional breakdown.

Fix is simple, just run: sudo chown username:username ~/.cache/*

Plasma developers should fix it in next release.