Today i upgraded my wordpress from 2.9.1 to 2.9.2 The upgrade process was pretty smooth. At first i had some trouble using the automatic update, so i ended up manually updating.
How to Manual Update:
The manual update process is quite simple. The wordpress website has full details on their website as to how to do this update. (http://codex.wordpress.org/Upgrading_WordPress) I will just go over the basics really fast.
Backup, Backup, Backup!
Any time you make a version change in WordPress you should backup your database. For that matter you should backup any thing you think is too important to loose any time you do something to wordpress. I dont know about you, but the idea of having to retype all my articles does not leave me with a warm fuzzy.
The Simplest way to perform this backup is through the wordpress export tool. This can be found under tools in your Administrative dashboard. Simply select to backup all users, and it will present you with an XML file containing all your posts, pages, comments, custom fields, categories, and tags. This is in no way a complete wordpress backup, but it should give you a backup of the important stuff. If you want a full backup you need to go into your database manager and backup your full database.
Also i suggest backing up your whole wordpress directory on your website. This is by all means not necessary, but i like to have backups of everything just in case.
Now its time to start the upgrade first you must make sure all your plugins are upgraded. This will help minimize the the chance of compatibility issues. Next Disable all your plugins. Just in case one of your plugins is not comparable with the upgrade, you don't want your site to be completely useless. If you forget to disable your plugins and have an issue after the upgrade you will need to manually disable them by either moving or deleting them from the plugins folder.
Download and extract, the latest update (http://wordpress.org/download/) locally to your computer. Open up your favorite FTP client (I Like FileZilla http://filezilla-project.org/) and connect to your web host. Delete or Rename the wp-includes and wp-admin folders in the root of your wordpress install. Then upload, replacing all the files, the new version on top of the old version. Dont worry you should not lose and of your config or data (if your worried make sure you backed it up.)
Once you have uploaded the files your all done. Now you can go to your website, and start testing functionality. Slowly turn on each plugin, and test that plugins features, to make sure its working, and not breaking something else.
Dont forget to test your website on both IE and FireFox.