System extended stored procedures (XP_CMDSHELL, etc.)
In high availability
Always On Availability Groups
Active Directory authentication
Extensible Key Management
Use of user-provided certificate for SSL or TLS
SQL Server Agent
SQL Server Browser
SQL Server R services
StreamInsight Analysis Services
Data Quality Services
Master Data Services
Here's a bit more clarification from the aforementioned Microsoft spokesperson:
"We are aiming squarely at feature parity over time, although some operating system specific elements in SQL Server which will be limited or unique for each operating system. There are a handful of features that will require more extensive integration and testing work with Linux and some of these features may be enabled post GA. We will prioritize these based on customer feedback.
"Most features of SQL Server are functions within the depth of the SQL engine and these features are all enabled in CTP1 because they have no interaction with the operating system or little interactions with the operating system and don't require any adjustments or additional testing. For example, ColumnStore, in-memory, query processing, transaction management and so on."