Installed the CVS Snapshot (2.2) of yesterday and the QuantityControllerV5_0.
When I wanted to checkout, I received an error saying that the function get_content_type() was undefined in order.php. I found out that get_content_type was original a function in shopping_cart.php class (included by application_top.php), but the function is missing in the QuantityControllerV5_0 shopping_cart.php class.
I've put the function get_content_type in my current shopping_cart.php and everything works fine. (I hope :)).