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.
Please visit the WLTC Plugin Competition Page and let Keith and I know what you think, and also check out the official plugin page.