It seems one thing is constant with WordPress and that is regular updates. Along with fixing and adding new functionality, security is one of the main reasons for updates to the WordPress core. To keep WordPress as secure as possible and to stay a step ahead of the hackers you should keep your WordPress sites up to date.
The automatic upgrade that is now part of WordPress, version 2.8.2 as of the time of this post, is, for the most part, a nice addition to keep WordPress up to date. There are some precautions that should be practiced no matter how you update WordPress.
WordPress Upgrade Precaution 1:
First is to backup and keeps a copy of the wp-content folder. The wp-content folder has your themes, plugins and uploads in it. The automatic upgrade should not overwrite these folders but I have seen cases when a customized default theme was overwritten.
WordPress Upgrade Precaution 2:
Next is the most important thing to backup and that is the database. The database holds the actual content and settings. Loose the database and loose it all!
WordPress Upgrade Precaution 3:
So do you need to go do this backup routine every time you upgrade WordPress? If you are doing a major upgrade from say version 2.5 to 2.8, then, by all means, you better backup and be ready for some issues especially if you have a lot of active plugins. I also recommend a manual upgrade for major jumps like that. But if doing a minor upgrade like 2.8.1 to 2.8.2 then I usually don’t backup anything and just do it automatically. When I say I don’t backup anything I mean I don’t do a manual backup right before the upgrade but I do have an automated backup that is no more than a few days old.
How to do a backup is entirely up to you but I strongly suggest you find a method and keep a regular backup schedule.