The latency due to nightly batch processing can be very costly to a business, both in capital expense and customer service terms.
Batch processing does not really fit the needs of a company that needs to run 24/7 in a global economy.
Refactoring to an ESB can provide a migration toward real-time data exchange, which removes the latency and reliability problems associated with ETL.
An ESB can be adopted incrementally, in a nonintrusive fashion by using special file-drop services that mimic the interfaces of the previous batch processing solutions.