The venerable schema_migrations table gets some new metadata in 0a5afa22, including a fingerprint and timestamp.
f02d2185 builds on this to add full migration history to schema.rb.
Active Record can use NOT in relation building as of de75af7ac, so you can say things like Customer.where.not(:name => 'Joe'). (The original commit also included LIKE support, but that was removed in 8d02afea5).
9d62e048 renames all action callbacks from *_filter to *_action. Seems like pointless jerking around to me, but whatever.