1. Intellisence Enhancements (IDE, Lookup will come automatically)
2. Declaration and Initialization in Same Line (Instead of DECLARE and SET in seperate Statement).
3. Compound Operators : (+=, -+, *=, /=....)
4. Multiple Value Insert in single Insert Statement
5. Grouping Sets (Grouping in Different Select stament is merged with one).
6. User-Defined Table Type and Table-Value Parameter (TVP)
7. New Date and Time Data Types
8. New Datatype DateTime2, DateTimeOffSet
9. HirerachyID

Ref : http://www.sqlservercentral.com/articles/SQL+Server+2008/65539/