You get 3 different client applications installed as dependancies of mir, my results are as follows...

First switch to a TTY.

Code:
(sleep 5; mir_demo_client_accelerated) & mir ; kill $!
Segfaults after reporting 'Surface created'.

Code:
(sleep 5; mir_demo_client_unaccelerated) & mir ; kill $!
Segfaults after reporting 'Surface created'.

Code:
(sleep 5; mir_demo_client) & mir ; kill $!
Runs without reporting any errors and exits cleanly, but nothing is displayed on screen.

I've had about 3 lots of upgrades to the relevant packages since adding the PPA yesterday, I'll report back when any new upgrades alter my results.