It was going to be called 7.5, but after adding so many features/changes it's now being called 8.0 and beta 1 has just been released.

Major changes in this release:

Win32 Native Server

This is the first PostgreSQL release to natively run on Microsoft Windows as a server. It can run as a Windows service. This release supports NT-based Windows releases like NT4, Win2k, XP, Win2003. Older releases like Windows 95, 98, and ME are not supported because these operating systems do not have the infrastructure to support PostgreSQL. A separate installer project has been created to ease installation on Windows:

Previous releases required the Unix emulation toolkit Cygwin for Win32 server support. PostgreSQL has always supported clients on Win32.

Savepoints Improve Transaction Control

Savepoints allow specific parts of a transaction to be aborted without affecting the remainder of the transaction. Prior releases had no such capability; there was no way to recover from a statement failure within a transaction except by aborting the whole transaction. This feature is valuable for application writers who require error recovery within a complex transaction.

Point-In-Time Recovery Increases Reliability

Though PostgreSQL is very reliable, in previous releases there was no way to recover from disk drive failure except to restore from a previous backup or use a standby replication server. Point-in-time recovery allows continuous backup of the server. You can recover either to the point of failure or to some transaction in the past.

Tablespaces Simplify Disk Layout

Tablespaces allow administrators to select the file systems used for storage of databases, schemas, tables, or indexes. This improves performance and control over disk space usage. Prior releases used initlocation and manual symlink management for such tasks.
Improved Buffer Management, CHECKPOINT, VACUUM

This release has a more intelligent buffer replacement strategy, which will make better use of available shared buffers and improve performance. The performance impact of vacuum and checkpoints is also lessened.

Change Column Types

A column's data type can now be changed with ALTER TABLE.

New Perl Server-Side Language

A new version of the plperl server-side language now supports a persistent shared storage area, triggers, returning records and arrays of records, and SPI calls to access the database.

COPY Handles Comma-Separated-Value Files

COPY can now read and write comma-separated-value (CSV) files. It has the flexibility to interpret non-standard quoting and separation characters too.
There's a ton of other stuff: