Took me about two hours to get Hibernate going the first time. Took me another two to port all my old JDBC code to the new mapping stuff. It adds about 5-10% to the runtime costs (which are pretty small to begin with). The cost was nil. Stuff that requires a lot of database interaction back and forth is done in a trigger or stored procedure.

Use a hammer for nails, a screwdriver for screws. This is the basic lesson you have yet to learn.