Many manufacturing companies', particularly those that use work cells, production process includes overlapping operations where an operation will start before the previous one is completely finished. For instance, a forge work center may have a work order for 200 units and the trimming operation that follows will start after the first 20 are complete.
Currently, scheduling is based on operations being completed sequentially. Adding support for overlapping or parallel operations will provide needed functionality. This has been a gap we have failed to overcome in several deals.