[Plugin: WP Super Cache] Question about Cache Rebuild

In the Advanced Settings, I see “Cache rebuild. Serve a supercache file to anonymous users while a new file is being generated. (Recommended)”

I’m not sure I understand how exactly this works.

Does that mean that every single time an anonymous user visits the page, he will be served a cached page, but a new cached version will be generated at the same time? If that’s so, doesn’t that defeat the purpose of caching?

I run a fairly popular site with about 200,000 page views per day, so needless to say that bandwidth and compute cycles cost me a little fortune every month. Would I be better off UNchecking this option?

Additionally, if I Check the “Only refresh current page when comments made” option, will the current page be refreshed if I edit it too?

I guess my goal is to never refresh a page unless it has been edited/updated by an Editor. Because I use Disqus for commenting, I’m not even sure that the “refresh if comment is made” option would work for me.

Could you please shed some light on this?

Thank you in advance

http://wordpress.org/extend/plugins/wp-super-cache/