WordPress developer team always try to catch up and fix bugs and security issues as soon as users report it. Although the updates release frequently, whether you want it or not, you must always do the upgrade to all of your WordPress powered sites.
Usually each upgrade has new bug fixes and security patches. So you must download the latest WordPress version and upgrade your WordPress after the download finished. Don’t delay the upgrade or you might will end up by getting a message by someone on your website.
But don’t think your WordPress site is safe just because you have upgraded it to the latest version. There are many ways the attackers can do to hack or to deface your website. So you must do the database backup daily (recommended) or at least weekly.
I have make a short article about how you can do the WordPress backup automatically by using a WordPress plugin. It is really simple to do and you will receive the backup file directly to your inbox.
My last note, if you not yet upgrade your WordPress to WordPress 2.2.1, I really suggest you to do the upgrade now.