Recs.
Updated
Xfce is a low resource user friendly desktop environment created for UNIX-like operating systems.
SpecsUpdate
Pros
Pro A true UNIX Desktop Environment
Xfce adheres to the UNIX philosophy, which means it strives for being modular, minimal and expandable. This makes it very much customizable. You can make it as minimal as you want and as heavyweight as you want depending on the features and modules/plugins you use.
Pro Adheres to standards
A priority of Xfce is adherence to standards, specifically those defined at freedesktop.org allowing for interoperability and shared technology for X Window System desktops. This interoperability is particularly significant for users looking to, e.g., run alternative window managers.
Pro Window manager (XFWM) is a compositing WM by default
By having a compositing WM as the default WM makes way for a lot of visual tweaks and tricks that can and do make Xfce look great. You can adjust the transparency, shadows, borders, etc. and many other advanced tweaks are also available.
Pro Excellent panel management and selection of panel applets
Xfce provides excellent management of panels and a rich selection of panel applets.
Cons
Con Now with Client Side decorations
Recent development versions introduce GNOME-ClientSideDecorations for some Xfce applications. Like on GNOME this breaks the overall consistency of the desktop. Eg: GNOME and some Xfce applicaions will use GNOME based interfaces like CSD's and popovers while the most other will use normal titlebars and popupmenus. This also makes it almost impossible to use Xfce >=4.15 components on traditional Window Managers like: Openbox, Fluxbox or IceWM.
Con Missing some basic functionality for a desktop environment
Xfce is missing essential functionality like a file-archiver, polkit-client or even a bluetooth or wifi managers, so you have to find alternatives for those applications (eg: by stealing them from MATE or GNOME, which adds additional dependencies that will bloat Xfce and makes it easily even heavier than GNOME).
Con Lacks modern design and effects
No support for transparency, effects in opening or closing a file browser, or other effects like cube or cylinder, unlike, say, KDE.
Con Looks dated
It just looks like a 20 year old desktop in its stock form. However, it is possible for you to to give it a more elegant look using themes, icons and other customizations.
Con Looks ugly out of the box
Out of the box, Xfce is the one of the ugliest if not the ugliest DE out there. It definitely can become the most beautiful and gorgeous DE after a bit of tinkering and theming, but the default theme is not that good.
Con Screen tearing issues
The built-in compositor for Xfce does not handle VSync, meaning that it does not address screen tearing for those with Intel integrated graphics. A third party solution will have to be used for those that do want VSync such as using Nvidia proprietary drivers to handle VSync or installing a third party compositor such as Compton.
Con Breaks standards
Sine 4.16 the developers ignore standards like the freedesktop icon naming scheme. Instead they now follow GNOME with rDNS icon naming breaking dozens of icon themes.
eg: gnome-calculator.svg becomes org.gnome.Calculator.png
rDNS naming also uses uppercase letters in filenames which is a bad idea on unix systems.
Con It doesn't support fn button for laptops
You can easily enable it, but it's not on out-of-the-box -> read comment.
Con Will become more interconnected an less modular
Isn't as modular anymore as it was 10 years ago. In the future (4.16) they will also introduce GTK Client Side Decorations to all setting dialogs so you will have some problems with using a different Window manager or when using xfce components outside of Xfce/GNOME.
Con One pixel wide window borders
The non-configurable, one pixel wide window borders make resizing difficult. Work-arounds exist but those are clunky at best.
Con Officially is no Longer the Champion of Lightweight Memory Usage
According to multiple credible sources in the Linux world and the KDE developers, XFCE now uses more memory than Plasma 5.17, due to Plasma bringing better and faster updates. Even the XFCE folks admit XFCE is somewhat getting out of hand.
I suppose this was tested on a minimal install of Plasma, without the entire KDE ecosystem. So if you are concerned with memory usage and use a "build-it-yourself" distribution like Arch, avoid XFCE and install Plasma by itself.
Con Too lightweight
Feels too lightweight and doesn't have enough packages and applications.
Recommendations
Comments
Flagged Pros + Cons
Con Very slow developement
XFCE tends to be extremely slow in it's development as it has been known to span years between major releases. While this means there are not many disturbing changes to the DE, it also means that new features that are requested take some time to appear.
Pro Classic and familiar
Xfce works very much like the classic Gnome & Windows desktops, taskbars (panels) and desktop icons, letting you get your work done without being frustrated.
Xfce embodies the traditional UNIX philosophy of modularity and re-usability. It consists of a number of components that provide the full functionality one can expect of a modern desktop environment. They are packaged separately and you can pick among the available packages to create the optimal personal working environment.
Pro HiDPI display support
It has HiDPI support, but requires adjusting settings. In Settings Manager β Settings Editor β xsettings β xft DPI can be adjusted. Setting it to around 180 should work well for "Retina" screens.
Out of Date Pros + Cons
Con No HiDPI support
Since Xfce is still based on GTK2 there is no HiDPI support (scaling UI elements).
Con Still uses GTK2
Porting to GTK3 has finished with release 4.14, so this con is no longer valid.