WordPress version 3.2 has finally been released with a plethora of great features.
You can see the official release note here: http://wordpress.org/news/2011/07/gershwin/
Here is a key snippet of text from the release note that you should keep in mind before upgrading:
Under the hood there have been a number of improvements, not the least of which is the streamlining enabled by our previously announced plan of retiring support for PHP4, older versions of MySQL, and legacy browsers like IE6, which allows us to take advantage of more features enabled by new technologies. The admin bar has a few more shortcuts to your most commonly-used actions. On the comment moderation screen, the new approve & reply feature speeds up your conversation management. You’ll notice in your first update after 3.2 that we’ll only be updating the files that have changed with each new release instead of every file in your WordPress installation, which makes updates significantly faster on all hosting platforms.
It is always a good idea to upgrade for security releases and better functionality and speed. As stated that PHP 4 and MySQL 4 and some web browsers are not longer supported, this is no reason not to upgrade, just make sure your server and web browser works before doing so.
Enjoy all the new features and the new look of the back-end!
List of all new features: http://codex.wordpress.org/Version_3.2