While I have no complaints about the SEO features of this plugin, I had problems with the sitemaps feature. It caused images to be indexed, which I did NOT want. I have that directory blocked in robots.txt, and I set the plugin to noindex media files. And yet, the sitemaps generated warnings in Webmaster Tools, somehow directing Google to look for images that had been deleted years ago. And then Google began indexing my current images, which again I did not want.
I asked for support over a week ago, carefully following the instructions to make my post just right, but never got a single response. I see a lot of other users getting similar warnings from Webmaster Tools, and in some cases it was easily solved but none of those solutions worked in my case. This has never happened with other sitemap plugins I used, so I've gone back to using those. There is something fundamentally wrong with the sitemaps functionality of Yoast's plugin, and it might be better to just remove that functionality if he is not going to support it.