Tante Ju, as the Ju-52 was affectionately known, was in many respects the Germans' DC-3. The planes did service on all German fronts. They were great transports but slow and underpowered for use in areas where the Luftwaffe did not hold air superiority.
While the three engines and corrugated metal sides engender comparisons with Ford's Tin Goose and the Fokker F-VII transports, both of those were smaller, high-wing designs while the Junkers was a low-wing plane.
Wikipedia [ http://en.wikipedia.org/wiki/Junkers_Ju_52 ] mentions that a bomber version was used in the Spanish Civil War and in the bombing of Warsaw. Green (Warplanes of the Third Reich) seems to state that the Spanish war bombers were all converted back to transports and that all the bomber versions built after the fall of 1937 were for foreign orders to Austria, Portugal and Switzerland. At any rate, it seems likely that no Ju-52s were used as bombers in any action against the Allies in Europe or Africa.