On Lubuntu, mir is running unimpeded with only one cursor on a fresh, daily, saucy desktop-i386.
Code:
ventrical@ventrical-P4M266A-8237:~$ ps afx | grep unity-system-compositor
2619 pts/0 S+ 0:00 \_ grep --color=auto unity-system-compositor
ventrical@ventrical-P4M266A-8237:~$ ps aux | grep unity-system-compositor
1000 2634 0.0 0.0 5664 816 pts/0 S+ 17:54 0:00 grep --color=auto unity-system-compositor
ventrical@ventrical-P4M266A-8237:~$ grep -i xmir /var/log/Xorg.0.log
[ 175.289] xorg-server 2:1.13.3+xmir1-0 (For technical support please see http://www.ubuntu.com/support)
ventrical@ventrical-P4M266A-8237:~$ ls -l /var/log/lightdm/unity-system-compositor.log
-rw------- 1 root root 110 Jul 1 17:48 /var/log/lightdm/unity-system-compositor.log
ventrical@ventrical-P4M266A-8237:~$
edit
hmmmm .. nope .. I don't think so because xorg is comming up in system monitor.
edit:
but all other indicators point that it is running ..