A must have plugin for a developer

I was looking for a plugin to let me create a copy of a site of great dimensions (db and files). The problem was to work on the new site mantaining it updated during the development with the dayly news and articles created on the live site.
With this plugin you can develop – even on a separate DB – doing nearly everything. From the creation of a new theme, to the update and the add of new plugins. You can upgrade WordPress too.
And If you have some doubts, the developer is very fast and professional in giving the answers!