With significant new functionality and performance enhancements, this release represents a major leap forward for PostgreSQL. This was made possible by a growing community that has dramatically accelerated the pace of development. This release adds the following major features:

Full text search is integrated into the core database system
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Support for the SQL/XML standard, including new operators and an XML data type
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Enumerated data types (ENUM)
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Arrays of composite types
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Universally Unique Identifier (UUID) data type
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Add control over whether NULLs sort first or last
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Updatable cursors
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Server configuration parameters can now be set on a per-function basis
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User-defined types can now have type modifiers
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Automatically re-plan cached queries when table definitions change or statistics are updated
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Numerous improvements in logging and statistics collection
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Support Security Service Provider Interface (SSPI) for authentication on Windows
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Support multiple concurrent autovacuum processes, and other autovacuum improvements
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Allow the whole PostgreSQL distribution to be compiled with Microsoft Visual C++

Major performance improvements are listed below. Most of these enhancements are automatic and do not require user changes or tuning:

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Asynchronous commit delays writes to WAL during transaction commit

Checkpoint writes can be spread over a longer time period to smooth the I/O spike during each checkpoint
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Heap-Only Tuples (HOT) accelerate space reuse for most UPDATEs and DELETEs
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Just-in-time background writer strategy improves disk write efficiency
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Using non-persistent transaction IDs for read-only transactions reduces overhead and VACUUM requirements
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Per-field and per-row storage overhead has been reduced
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Large sequential scans no longer force out frequently used cached pages
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Concurrent large sequential scans can now share disk reads
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ORDER BY ... LIMIT can be done without sorting

The above items are explained in more detail in the sections below.