I know the title says "in brief", but it's a little too brief for me. From the horse's mouth:

http://www.varnish-software.com/blog/varnish-30-changes-esi-...

http://www.varnish-software.com/blog/bans-and-purges-varnish...

http://www.varnish-software.com/blog/streaming-varnish-30

Something to pay attention to from that streaming post: if the asset you're streaming isn't already in the varnish cache, only the first user to request it will get it streamed. All other clients will be blocked until the first stream is complete and cached.

> The object will be set to busy while it is streamed. Other clients will be put on hold. Furthermore, the rate at which the object is fetched by the client dictates how fast Varnish will fetch it from the backend.

Unless I'm reading the above wrong, [re-warming your cache for these large objects would seem more prudent than relying on streaming.

There's also a nice write-up by Redpill Linpro employee and Varnish contributor Kristian Lyngstøl:

http://kristianlyng.wordpress.com/2011/06/09/varnish-3-0-0-r...