Oracle's complexity and vendor lock-in is a minus to the extent that if there is *any* other way to solve the problem, including using MS-SQL, Sybase, or even DB2, use the alternative.
My employer has been using AIX for stability reasons for a long time (since the very early 90s). At the moment neither MySQL nor Postgres guarantee AIX ODBC driver support. Only DB2 (obviously), Oracle and Sybase (IIRC) do that so there you are, another reason on to keep dealing with these companies. Whether you use MS-SQL, Sybase, or even DB2 is really irrelevant, they all force a degree of vendor locking, they are expensive and come to think of it, if you want support, MySQL is merely somewhat less expensive than the rest. I will agree that Oracle's pricing is armed robbery but they are not alone. I had a one third party driver vendor ask more money for a MySQL ODBC driver license for AIX (that allowed us to connect to one MySQL instance) than it cost to get a MySQL enterprise license. It was cheaper to migrate to DB2.