Since then, I've found it to be an essential app. And it's particularly useful for working with Drupal. Specifically: for syncing local Drupal sites across multiple systems. And for sharing access to said Drupal sites with other developers.
So here's a quick guide on how to setup a really slick Drupal testing environment. One that will sync across multiple systems and enable quick access for your development partners.
Integrating XAMPP and Dropbox
First thing's first: you'll need a local server. And the easiest way to get an apache server setup is to use XAMPP.
Once you have XAMPP installed, the key to making it integrate with your Dropbox - is to change the default path of your "htdocs" directory to a folder within your Dropbox account.
By default, the file to modify is located at "xampp\apache\conf\httpd.conf". Then find the line called "DocumentRoot" and change it to something such as "C:/My Dropbox/htdocs". And a few lines down there is another entry called <Directory "..."> that you will need to update with the same path. Done!
Syncing your Drupal databases
You'll run into potential problems if you use Dropbox to sync your MySQL - so the best way to sync your Drupal databases across multiple systems is to use MySQL replication. I found a simple guide on how to setup MySQL replication here.