On December 11, 2012, WordPress released version 3.5, naming it after Elvin Jones. Elvin Jones was a jazz musician who played the drums. If you wish to learn more about him, you can read up about Elvin Jones on Wikipedia.
WordPress 3.5 comes with several great updates. One of the ones I have been really rooting on what the development of a better Media Library. Previous version was a multiple drag and drop upload ability that still had somewhat the same flavor as even older media library version’s within WordPress. The upload interface after clicking add Media from a post or page is much different.
As you can see, the area of the upload when you click to add new media is a lot bigger, spanning most of the screen.
When you add new files, instead of a one column, the images are shown in several columns, as well as file type.
Other user interface have been tweaked to be cleaner. For developers, there are some goodies like a new importer from Tumblr to WordPress, and installing blogs faster and better in multi-site.
WordPress has also introduced a new theme that is not your usual blog format theme. Not everyone runs a blog for the focal point of their site, and so, since WordPress is a full content management system, so the theme Twenty Twelve is a great example of a basic CMS type site. Twenty Twelve is also mobile responsive!
If you are worried about updating your site to the new version due to hearing some upgrades gone a little hairy, it might not happen to you. It may be a conflict from a plugin or theme you are using. Each release is tested by many people, from user to intermediate code savvy, and to even hard core developers.
As a reminder, before you upgrade your site, back it up!!!
If you are not sure, either install a beta version of your site and try the upgrade, or install it locally on your computer and try it out. If you are having issues you can use the WordPress Support Forums to submit the issue. Those who are developers, and the issue is deeper, like a bug found, you can submit a ticket in WordPress Core Trac.
You can find out more on WordPress 3.5 release at from WordPress.org.