I have a store I'm developing that has two store views, one for each language I'm supporting. The products and categories have localized url keys.
In 1.7.0.2 my language switcher would redirect correctly (for ones that had "Create Permanent Redirect" as well as ones with out) but after upgrading to 1.8.0.0, it did not work any more.
Problem
There is a regression in 1.8.0.0, they updated Mage_Core_Controller_Varien_Front to use ::_getRequestRewriteController()
in ::dispatch()
previously it used Mage_Core_Model_Url_Rewrite and now it uses Mage_Core_Model_Url_Rewrite_Request
On line 143 of app/code/core/Mage/Core/Model/Url/Rewrite/Request.php it has $stores = $this->_app->getStores();
which returns an array of store_id index stores, but it goes on to check if the store it goes on to check with $fromStore, which is a variable from the GET params, ___from_store, which contains the store views key (e.g. default, french, etc), obviously this has problems looking up using a alpha key in a numericly index array.