With the imminent release of Drupal 7.0 in the next few hours, you may be asking yourself what it's all about, and do I, or should I, upgrade my Drupal 6.x site to Drupal 7.0.
Drupal 7.0 comes with a whole host of revolutionary changes over Drupal 6.x, including a new overlay administrator interface, custom content type support built in, reorganised administrator architecture, live web module & theme installs, various usability enhancements and more. Additionally, the Application Programmer Interfaces, or API's, available in Drupal 7.0 to module and theme developers, have all been re-designed and re-written to allow for higher quality, more functional, more portable 3rd party modules and themes.
Unlike previous Drupal releases, an effort was made during the early development versions of Drupal 7.0 to ensure 3rd party Drupal module developers  had compatible Drupal 7.0 versions of their modules available on official release date. So thankfully, a lot of a modules your site may use, are already Drupal 7.0 ready.
Itomic are already using Drupal 7.0 for internal website projects, and are planning to begin building basic brochure Drupal sites in version 7.0 over the coming weeks, so keep an eye open here for our first Drupal 7.0 site . As for larger sites, i.e. those using more then a dozen 3rd party modules, and any custom modules, we'd be recommending waiting 3-6 months before considering the change over.
You may ask, why upgrade at all? New Drupal functionality, in the form of 3rd party modules, are released almost daily. Whilst this new functionality may not be helpful to your site, eventually some of it will be, and eventually you'll want to be able to use it. New modules have a tendency to only be written in the current version of Drupal, so if you're still on the previous version, you may find you can't use it until you upgrade.
The Drupal development team will continue providing Bug and Security fixes for Drupal 6.x core, up until the day Drupal 8.0 is released - which as per previous Drupal release cycles, will be at least another 2 years away. So at a minimum, you'll want to at least upgrade before this time.
You can download your own copy of the latest release candidate at drupal.org , or wait a few more hours, and the official version 7.0  will be available. In the meantime, lookout for the Drupal 7.0 release celebrations  happening around the world.