Looks like upgrading to WordPress 2.6 from 2.5.1 is really easy. Delete a wp-admin and wp-includes directories, save your old wp-config.php file, upload new files, copy values from old wp-config.php file into new file, go to admin screen to do a quick database upgrade, and wha-la, you’re done! Hopefully everyone has had the same experience I’ve had, and no one has had to completely reinstall WordPress like I had to awhile back (what a pain!). Here’s some instructions on upgrading to WordPress 2.6 in case you can’t find it:
And here’s a little about new features and whatnot in WordPress 2.6
See this video and more here.
You may want to try out the WordPress Auto Upgrade Plugin which speeds up the upgrade process.
http://wordpress.org/extend/plugins/wordpress-automatic-upgrade/
Ooh, cool plugin. I d/led something similar awhile back for plugins, didn’t know they had one for the entire installation. I’ll give it a whirl!