Just look at new features:
- Greatly improved performance consistency, through HOT, Load Distributed Checkpoint, JIT bgwriter, Asynchronous Commit, and other features.
- TSearch2 full text search integrated into the core code with improved syntax and ease of adding custom dictionaries.
- SQL:XML syntax.
- Logging to database-loadable CSV files.
- Automated rebuilding of cached plans.
- ENUMs, UUIDs and arrays of complex types.
- GSSAPI and SSPI authentication support.
- … and many others