I've put a draft version 0.2 of RVW online, to be used in feeds for syndicating and aggregating reviews. If you're thinking of producing reviews from your site, please have a look and see whether it includes everything needed to pass on all the required information to aggregators.
The main changes from the last version are rvw:rating (a percentage score, which is the same rating scale that iTunes converts to for storage) and using the simpler, but hopefully flexible enough, dc:subject for categorisation.
I've also extended the data to fit in Atom, RSS2 and RDF (the RDF has two examples, as it's possible to produce either a list of reviews - eg an RSS1 feed - or a list of reviewed items - eg a playlist).
I'll add some more definitions and descriptions of each part once I'm sure the syntax is correct.