I´ve used this plugin on a few blogs, both in shared hosting environments and on my own VPS and the plugin works perfectly out of the box.
Just make sure you have enough memory and run a reasonably modern version of PHP.
The interface is really nice, you can select the folders or subfolders you want to exclude from backup.
The first backup might take a while, as all folders and files are transferred to Dropbox. Later sessions only new or changed files are uploaded.
Big thanks to the author.