Over use/correct use of schemas?
Schemas are not only a great security tool (which is reason enough to use them), but they are also perfect for logical separation.  And it seems as though this is what you are practicing.

Even if the current requirement doesn't need special security, say down the road all of the database objects that are related to Auditing should be secure to a database role.  If these objects were scattered throughout the dbo schema, then you would have to explicitly deny permissions on the individual objects.  But with the Audit schema, you do a single deny and you're set.

I personally practice the use of schemas.  Like all things in databases, though, there is a happy medium.  I wouldn't create a schema for each granular aspect of the data layer.  There is such thing as too many schemas and separation.  But I'm guessing you aren't anywhere close to that.