How many other fields may a custom lead field be mapped to when converting a lead?

Determine if the description is Master/Detail or Lookup: Lookup field on child is always required.

Is it possible to report on the converted Leads?

How many fields (columns) can be displayed on a Customizable Related List?

Workflow rules are triggered when a standard object in a master-detail relationship is re-parented, even if the object's evaluation criteria is set to When a record is created, or when a record is edited and did not previously meet the rule criteria.