One of the side projects I’ve been working on of late is helping Keith Dsouza automate a plugin to automatically upgrade your WordPress installations. The plugin is still young in development, but it provides a groovy one-click WP upgrade. I personally tested it on versions of WP as early as 1.5.2 and as late as 2.2.1. Give it a try and see if it works out for you. Who knows, it might make your job with clients easier when it comes to updating their installations.