Here is a summarised list of new features in SQL Server 2014 that could be worth an upgrade. There are still a lot of customers on SQL Server 2008, they could take the path straight to 2014 instead of going to SQL Server 2012.
1. New In-Memory OLTP Engine
2. Enhanced Windows Server Integration
3. Enhancements to AlwaysOn Availability Groups
4. Enhancements to Backups
5. Updateable ColumnStore Indexes
6. SQL Server Data Tools for Business Intelligence
7. PowerBI for Office 365 Integration
The New-In Memory OLTP Engine and ColumnStore Indexes are bound to attract the OLTP and OLAP Customer base. Please read through these feature details in the following link. The link gives a more detailed description of the features.