Recs.
Updated
SpecsUpdate
Pros
Pro Plugins can be used to bypass Windows mixer to output a bit-exact signal
Through the use of a plugin (of which there are three popular ones), users can get bit-exact sound output straight to their DAC or soundcard. While not something every user will use, for audiophiles this is a pretty important feature.
Pro Functionality can be extended with components
Foobar200 has over a hundred components to choose from that add UI functionality, decoding support for various formats, etc.
Cons
Con Locks files and folders, making it hard to manage them
Several parts of Foobar lock files and folders in a way that they cannot be file-managed (move/copy/rename/delete) easily in the program (and externally). With the waveform plugin it's even worse. Cannot delete a file until the waveform is fully scanned.
Con Outdated Plugins
Many, many plugins are outdated and not maintained for years, leading to stability issues with a lof of them. A rather complex SDK and missing sufficient documentation makes maintaining or creating new plugins unnecessarily hard.
Getting to that neat GUI setup you've seen somewhere is probably impossible because of that.