I'm using it on a daily base for development and as a server plattform.
9vx is my terminal, while I use geany editor from linux as an editor. 9p filesystems can easily be started for data transfer with native 9legacy. The only feature I miss in 9vx is the lack of some plan9 devices in my case the #g (segment) device which I use for shared memory on 9legacy forks to create my graphical framebuffer and font infrastructure. But there is a simple workaround for this problem so I don't mind it too much.
9vx is extremly fast I can compile the kernel and userland in less than 2 minutes and the greatest advantage is the ability to use the underlying host filesystem directly from within linux.
When I started kernel development with 9legacy after the licence changes I was looking for some way to exchange data between host and guest when someone pointed me to 9vx and afterwards it became my "thats it" solution.