What features in ESS do I need to use/set up/know about?

I'm currently running the trial version of ESS on one of my computers. I'm relatively happy with it so far, although at first it seemed to block all incoming and outgoing internet connections, but it seemed to solve itself and I can't work out why or how.

Anyway, what features in ESS do I need to tell people about when setting it up on other people's computers?

Can I just install it and leave it running without changing any of the default settings? Are there any settings that should be changed after installation?

How does the antispam module work? Do I have to manually enter addresses into the program's blacklist, or can my email program do that for me?