Recs.
Updated
SpecsUpdate
Pros
Pro Has a file manager that provides a good balance between power and simplicity
The included file manager provides several icon, list and detail views to choose from along with features such as tabs, bookmarks, tagging, previews and metadata, network file access, bluetooth file transfers to/from devices and excellent removable storage integration while remaining fast and easy to use.
Pro Adheres to standards
Standards adherence allows for interoperability and shared technology for X Window System desktops, with similar Wayland support being worked on. Applications not written with Plasma in mind work very well in Plasma as a result. The development team has also been instrumental in standard creation and adoption such as NETWM, X11 clipboard, icon themes, mimetype handling, application menu standardization, system tray protocols and notifications and more.
Pro Comes with a suite of powerful applications
Plasma Desktop generally comes packaged with a full set of applications to get users started, including a file manager (Dolphin), advanced file manager and browser (Konqueror), image and document viewers (Gwenview, Okular), the Calligra office suite, CD and DVD authoring (K3b), and dozens more. The desktop can be installed and used without these applications, but they add significant value for many people.
Pro Very customizable
One of the best aspects of KDE is that it gives you Lego-like tools called widgets. You can combine the widgets in the way that better fits you and get a Mac OS desktop layout, a Gnome 3 desktop layout, a mobile device desktop layout or a completely new desktop layout that works for you.
Pro Simple by default, powerful when needed!
For the new Linux users (coming from windows), they'll find everything easy and simple to use!
But for old and experienced linux users, they can customize the interface as they want!
That's why Plasma KDE, Simple by default, powerful when needed!
Cons
Con So complex and full-featured that makes you feel lost easily
The fact you have tons of options to customize the DE makes it more confuse and complex, so you can get lost easily. Questions like: Where the X thing is? How to disable the single-click? It can make somebody that is used to the simplicity of Gnome or Xfce very confused.
Con No easy way to backup & restore all settings
Most crashes cause loss of settings - panels vanish, all favorites and launchers missing, icons lost, wallpaper back to default, theme changes, activities present but not active, etc.
The configuration is held in a multitude of places, the changes are applied automatically even after a crash, all without a tool or clear way to recover.
Con HiDPI support is spotty
The log in screen as well as some other components of the OS do not scale properly under HIDPI. Some things in the log in screen will be displayed too small, such as the mouse pointer. It can also be difficult to get full scaling to work properly in the DE itself with things such as icons, text and window borders.