ODBCDirect is an acceptable choice if your application must run queries or stored procedures against an ODBC relational database, or if your application needs only the specific capabilities of ODBC, such as batch updates or asynchronous queries. It's worth noting, however, that every feature in ODBCDirect is also available in ADO.
If you have a working knowledge of ODBCDirect (or its look-alike DAO), and have large amounts of existing ODBCDirect code, or just need to extend an existing application that already uses it, ODBCDirect will still work for you. The drawback is that as your application requires other types of non-ODBC data sources, ODBCDirect cannot provide data access. Eventually, you'll want to take advantage of the design, coding, and performance benefits provided by ADO.