unionfs-fuse is a unionfs filesystem implementation using fuse.
It is meant to be way more flexible than the current in-kernel unionfs solution.

Why choose this stuff?
 * The filesystem has to be mounted after the roots are mounted when using the standard module.
   With unionfs-fuse, you can mount the roots later and their contents will appear seamlesly
 * You get caching (provided by the underlying FUSE page cache) which speeds things up a lot for free
 * Advanced features like copy-on-write and more

Why NOT choose it?
 * Compared to kernel-space solution we need lots of useless context switches which makes
   kernel-only solution clear speed-winner