Update Network - doesn't tell you what version your network is running

This page is where I update the network, which I understand is a separate function from upgrading the software:

wp-admin/network/upgrade.php

I updated to WP 3.4.2 and then went to the above page and clicked Update Network, which I guess makes 3.4.2 available for my sites.

When I go back to the upgrade.php page, I can't tell if I have already upgraded. Is there a way to determine what version the network is running? If not, this page seems like the place for that information. Can different sites run different versions of WP?

Just trying to help.

Thanks,
James