Currently R# 2.5.x does not handle "extern alias".
The behavior I have noticed is that reformatting creates a broken line (extern + CR/LF + Tab + alias) at the end of the using statements. As you may know, extern alias lines must appear before using statements.
Intellisense stops working for any type names that colliding with the aliased namespace. Our use of extern alias is to remove some type names from the global namespace that are conflicting with commonly used type names.
Does anyone know if there exists a version of R# that can properly handle "extern alias". Upgrading to 3.x is a completely acceptable answer - as long as it works.