Given that Tomcat 6.0 is in a pre-release state, you'd be better off
asking in the development list (dev@tomcat.apache.org). Maybe the
documentation developer will see your note and can tell you when the
docs will be updated.
Your best bet is probably to get the source and start playing with it.
You may also want to take a look at Terracotta Sessions. They just open
sourced their product today.
http://www.terracotta.org/confluence/display/docs22/Terracotta+Sessions+
Quick+Start+Guide
The listed Tomcat versions supported are:
5.5.20
5.0.28
That's not to say their product won't work
