Two days ago, WordPress 3.1.1 has been released. This is a maintenance and security release that fixes almost thirty issues from the 3.1 version.
Whether you have already upgraded to WordPress 3.1 or not, this is the best time to download and update to the latest version of WordPress 3.1.1, or you can automatically update via your WordPress admin panel. I personally prefer to do the update manually because the automatic update always fails for me.
Before you do the update: it is always safer to do a complete backup, in case something goes wrong.
After the update: test your Website to make sure that everything, including all your plugins, are working normally.