WordPress released version 2.5 today. In the past, I’ve put off upgrading because it was such a hassle. Unfortunately, that makes a site vulnerable to security exploits. But I just upgraded both sites running on this server, and it took a total of about two minutes each, thanks to WordPress Automatic Upgrade. From the description of the plugin:
allows a user to automatically upgrade the wordpress installation to the latest one provided by wordpress.org using the 5 steps provided in the wordpress upgrade instructions.
Really, really simple. I used version 0.8, which was already on my servers, and I had to go back in after the upgrade was complete to enable a few other plugins. I suspect if I had downloaded WAU v 1.0 first, that would have been a non-issue.
If you use WordPress, this plugin is a must.
Ed Bott (@ wordpress.com) 
I’ve used it the last 2 upgrades with great success. I am having a problem with the automatic upgrades for the plugins though. I get a fatal error, which I’m going to submit to wordpress.org. In the meantime I’ll check my hosts servers and see if it’s something in their settings.
Oh it’s brilliant alright! I used it to upgrade mine from RC3 and it worked flawlessly.
I download the latest Version WAU v 1.0 and everything went well with the exception of the re-activate plugins. Great tool. Completed the update to four blogs in a very short time.
I found the problem with the updating of the plugins. WP Auto Updater also got an upgrade from .80 to 1.0. Once I updated it the plugins went through the auto update without a problem.
I used WPAU 1.0 to upgrade my blog, and like others I had to go back and manually activate the plug-ins. No biggie. It was an otherwise flawless process.