I use both FreeBSD and Debian-based Linuxes on a daily basis. (I am mostly a user/developer/sysadmin not an OS-developer).
I want to know what is the motivation behind kFreeBSD? Why people may want to use FreeBSD kernel but avoid the user land?
All of the following reasons, are the benefits you get from the FreeBSD kernel:
Why would you prefer Debian GNU/kFreeBSD to FreeBSD?
From the official wiki, there you can find more points on why to prefer the Debian GNU/Linux and not be totally FreeBSD.
There are several reasons to avoid FreeBSD userland:
In no way I am criticizing either of the operating systems. Both serve their purpose well. kfreeBSD is an attempt to combine best of both worlds.