Hi,
There are lot of threads related to this topic, please search before post this thread.
LSMW will use to migrate the legacy data to SAP System, It is purely used by the consultants for legacy migration. It will use more in implementations and Rollouts, In the support it is better to create BDC to the user perspective, LSMW has couple of steps and users are bit hesitant to execute these many steps.
Regards,
Ravi