Can I see who else is connected?

Yes. Currently connected users can be monitored from the VNC Server Information Center dialog, and disconnected if necessary:

By default, the VNC Server user is notified when VNC Viewer users connect and disconnect:

You can turn this notification system off from the VNC Server Options dialog if you wish:

Alternatively, you can configure VNC Server to always display the name of the connected user, or most recently connected user, by changing the 'ConnNotifyAlways' parameter to True either in the Options > Expert dialog box or at the command line.