That last post made me realize I hadn’t mentioned one of the biggest changes to Magento 2: No more class aliases.
Magento still has factory methods for instantiating objects, but instead of the shorter, more elegant, and confusing class aliases
Mage::getModel('catalog/product');
You use a full PHP class name
Mage::getModel('Mage_Core_Model_Product');
Class rewrites are still available — this just removes one level of complexity from the configuration (where you need to specify a base class name to use for an alias group).
This is probably the right choice, but I’ll miss class aliases — under the hood they may have been complicated but for day to day programming they were an elegant solution for a namespace-less PHP.