Although many things changed throughout milestone builds of 2.0, we wanted to call out one thing in particular.
As of the 2.0 GA release, the "owning" table for default sku : default product relationship has changed. Previously, the BLC_PRODUCT table contained a DEFAULT_SKU_ID column. Now, this relationship is keyed by the DEFAULT_PRODUCT_ID column in the BLC_SKU table.
You can run the following script AT YOUR OWN RISK to update your tables if you are moving from a version prior to GA to GA.
UPDATE BLC_SKU AS sku SET sku.DEFAULT_PRODUCT_ID = (SELECT PRODUCT_ID FROM BLC_PRODUCT WHERE DEFAULT_SKU_ID = sku.SKU_ID)
You'll also want to remove the DEFAULT_SKU_ID column from BLC_PRODUCT, as it is no longer used, and its continued presence can cause problems.