Oh and the really big caveat I just forgot about:
http://download-west.oracle.com/docs/cd/A87860_01/doc/server.817/a76992/optimops.htm
says:
The optimizer can merge a view into a referencing query block when the view has one or more base tables, provided the view does not contain the following:
* Set operators (UNION, UNION ALL, INTERSECT, MINUS)
* A CONNECT BY clause
* A ROWNUM pseudocolumn
* Aggregate functions (AVG, COUNT, MAX, MIN, SUM) in the select list
