CTP 3.3 is now generally available:
In SQL Server 2016 CTP 3.3, available for download or in an Azure VM today, some of the key improvements include:
Continued enhancement of Stretch Database: Stretch Database allows you to stretch operational tables in a secure manner into Azure for cost-effective historic data availability. CTP 3.3 includes multiple improvements to Stretch Database, including Azure Stretch database edition preview with support for up to 60TB, Point-in-time restore and geo-failover support.
Enhancements to In-Memory OLTP: In-Memory OLTP, which dramatically improves transaction processing performance, has added support in CTP 3.3.
Enhancements to Analysis Services DirectQuery models: Analysis Services Tabular Models running in DirectQuery mode now also allows us of DAX filters when defining roles and creation of calculated columns.
Enhancements to the new Reporting Services web portal: An updated preview of the new web portal now enables you to add the KPIs and reports you use to your Favorites, to create and edit shared data sources for your KPIs and reports, and to perform other management tasks.
Admittedly, none of those strikes me as compelling “must-download” reasons but the technical overview does have some more details.