This plugin allows you to transfer your inputs SEO data from one theme/plugin to another.
Probably. If it is a paid theme or plugin, the author will have to provide a copy for us to analyze. If it's free, and demand is high enough, we'll include it.
It's relatively stable. This plugin has been in the repository since August, 2010, and no one has reported any problems. As always, be sure to keep a backup of your site, just to be safe.