Ian Giblin, one of the awesome dudes on the Illustrator team posted a nice tutorial on using the Recolor Artwork feature in Illustrator (CS3 and CS4). Brenda Sutherland, one of the awesome dudettes on the Illustrator also recently posted some great information on the feature as well over at Infinite Resolution, which is the Illustrator team's new blog. Take a look! Hopefully we'll see lots of great stuff there.
Just as an FYI, I recently completed an in-depth article on how to use the Recolor Artwork feature for iStockPhoto. Once the article is live, I'll post a link to it.