I tend to be the cautious type with such matters, and I have an excellent piece of software that lets you provide multiple variations for words / sentences etc, and in layers, to give a lot of variations on articles.
I'm curious how often, and how thoroughly you guys spin your articles that you submit to multiple sites. I so far am just submitting to 10 or so directories that have some page rank, with my original draft going to ezine articles.
I've heard that duplicate content is not really that important.. having heard examples of a huge news story that were to break, which gets reposted millions of times without google suddenly 'blocking' that article. I'm curious your thoughts or experience with this!