I'm working on the docs this week. Now that AS7.0.1 is out the door, the docs should be complete by the end of the week.
The best place to get started (for now) is probably this webinar that I gave on AS7 clustering:
AS7 clustering is definitely not production ready. There are several components that are still in development. Some details here:
Some details about the use of Infinispan in AS7 can be found here:
Clustering should be feature complete by AS 7.1. If that fits in your timeframe, I would encourage you to go that route, since the next EAP release (EAP6) will be based on AS7.1, not AS6.
As far as clustering in AS6, the AS5 docs are all relevant with 1 major difference. AS6 replaced JBoss Cache (the distributed caching solution upon which most AS clustering services are based) with Infinispan. This in really an implementation detail, that you only need to be aware of if customizing the default clustering bahavior, and is documented here: