We moved a million posts to XF from our old system last week - up and running by Thursday evening. For those worried about SEO, I have the following to report...less than one week later, we are largely whole. Google appears to have the site and all the posts re-indexed....and we have redirects in case they don't (and for external sites with links to our forums). Note that the new url is hearth.com/talk - and see the enclosed screens. Google has the main site as well as the forum rooms in fine order. Also, our site traffic (page views) returned to normal within 3 days. Since we had the old forum set to read-only for a day of that, it is quite impressive. I will report further when there is more data to share.