Not much, unless you consider the below items important:
- Enterprise Readiness – support for up to 500,000 Active Directory User Objects (up from 20,000)
- Recycle Bin Enhancements – Now the Recycle Bin and management of it will be available in the SharePoint Administration Center
- PDFs – PDF documents will open directly without requiring a download first
- External Sharing – Now you will be able to invite any external user to participate on your site, up until now they have to have an email with the live.com, msn.com or hostmail.com domain
Read more about these new features and improvements here!