Myth: ODBMSs Have a Steep Learning Curve
The myth that ODBMSs have a steep learning curve is easily dispelled. Using an ODBMS primarily involves knowing an object programming language. For examples, see transparent persistence.
If you know Java or C++, there is very little additional syntax that you need to learn in order to use an ODBMS. There are additional database commands for opening and closing databases along with starting and committing transactions. But that is about all -- hardly a steep learning curve. If you do not know Java or C++, there is learning involved. That learning, however, involves mastering the programming language and not the ODBMS.
If you have never used an RDBMS or an ODBMS, you will need to understand basic concepts about transactions and units of work. This learning will be needed regardless of whether you are using and ODBMS or an RDBMS. See the DBMS ACID Properties.
One could argue that the learning curve is much higher for SQL-based interfaces (SQL-92, JDBC, SQLJ, SQL:1999) than for transparent persistence interfaces (ODMG 3.0 and JDO). This could be based simply on the length of the texts needed to explain each interface.
More on the general topic: ODBMS Myths