Pumpers are great for the reasons already stated. Set the engine for maximum performance and forget about nose up tests, etc... the pump keeps things going.

Most Gasoline engines have a built in fuel pump as a point of reference.

As stated rebuilding the pump adds a small degree of complexity, and some additional cost... plus it is one more thing that can go wrong ( hint: FUEL FILTERS help keep debris out of the pump ).

However I really like them.