WordPress 3.5 was just released and the biggest change that most WordPress website owners will notice is the dramatically changed media center. The media uploader has been completely rebuilt and now makes many tasks much simpler, including creating and managing new galleries.
Here’s a video overview from the WordPress.org blog highlighting 3.5:
Remember to completely back up your database and files before upgrading your WordPress site.
Also, with WordPress 3.5 (a major release) I have noticed that numerous plugins we use are also issuing compatibility updates, so be use to update those as well.