What are peoples thoughts on Content Microsites to help build SEO?

I did it to help my wife's business rank number one for her main keyword in our local area which has driven a decent amount of business.

Bottom line is it works and don't get caught by Google. I found a good expired domain with some links from lots of blogs and even a newspaper and setup a site. Even just that one site boosted rankings significantly. I did my best to make it as high quality and believable as possible though I once spotted a guy doing this in the wild and it was very obvious and poor quality. So, yes you can do it, yes it works, yes it has risks and if you do it do it so high quality that those microsites can be real sites that add value in their own right.