Drupal 7 alpha version was released about two months ago.Drupal has released the seventh (and hopefully final) alpha version of Drupal 7.x for your further testing and feedback.
This release includes:
# HUGE number of upgrade path fixes, including automated tests for updates.
# Great usability improvements, including the installer not greeting you with a red error of death anymore on shared hosts!
# Field UI improvements to allow it to be further extended from contrib.
# Numerous Form API fixes and improvements.
# Numerous accessibility fixes.
# A variety of PostgreSQL and SQLite fixes, almost at 100% automated tests passing on both!
# Lots of polish on coding standards compliance and API documentation.
# Markup improvements, and a new default jQuery UI theme.
# Numerous security fixes, including 'forward-ports' of Drupal core SAs, and fixes to private files.
# Performance improvements.
For more check out this link http://drupal.org/drupal-7.0-alpha7