To answer your question, I'm a user of KDE since its 3.x days. KDE 4 was as bad as they say it was - buggy, terrible theming and impaired customizability. The s

To answer your question, I'm a user of KDE since its 3.x days. KDE 4 was as bad as they say it was - buggy, terrible theming and impaired customizability. The stability did improve in its later versions though. I switched to Plasma 5 about a year ago, when the first stable version landed on Arch linux. It's been a daily driver since. Initial versions had lots of bugs in them - persistently high CPU usage. Sometimes the desktop hung for no fault of the user. Proper resumption after standby/resume was a lottery. On the plus side, the Breeze theme was a breath of fresh air compared to the older Oxygen theme. Since version 5.6 was released things have improved and keep getting better with every new version. There are still occasional cockups with Intel graphics drivers leading to high CPU usage. The problem though seems to stem from the Qt libraries. Some GTK 3.x apps don't show proper widgets (blame Gnome devs for not having consistent themes for 3.x versions). I did give other DE's a go - Gnome 3.xx, Cinnamon, XFCE etc., but always ended up switching back. Plasma offered the best mix of customizability, performance and aesthetic appeal for me.