The demo site ( http://www.try-phpbb.com/31x/ ) is currently at 3.1.0. Since 3.1.2 incorporated quite a number of bug fixes, the demo should be updated.

Seeing a big red "Your phpBB installation is not up to date." does not present a good impression.

In the General tab, I also see this warning "Please delete, move or rename the install directory before you use your board. If this directory is still present, only the Administration Control Panel (ACP) will be accessible.", but the board is functioning.