If you want to buy a gallery with good SEO results. Don't use Nextgen. I've used the build in image gallery of wordpress in a previous install and this works way better than Nextgen gallery. Developers: please do something, the plugin looks great and works easy in the backend, but the most important thing is being find with tags, titles and descriptions in Google. Seo by yoast only adds an sitemap, but the real seo problem is within the core of the Nextgen gallery.
I hope there is somebody watching from the Nextgen developers team. I'm not the only one complaining about this on the internet. I'm willing 2 pay for a good seo add on the nextgen plugin