Rob Sbaglia on "[Plugin: W3 Total Cache] I'm new to this - how do I know it is working?"

Hi,
I'm new to this idea of caching. I've installed the plugin (although I didn't change the permissions before installing). It says it is working, but is there some difference I should see?
I haven't altered any of the settings - do I need to alter a setting after installation to see an effect?
Cheers,
Rob.

http://wordpress.org/extend/plugins/w3-total-cache/