As Hildesheim was destroyed by bombing in late March 1945 the town generally still suffers from that. At the world heritage site, there are big reconstruction works going on(2012) and is not tourist friendly. Planned to end 2015, so i recommend to wait until 2016 for a visit.
Don't miss to walk the "Kulturweg auf den Rosenroute" which leads you through the rest of what is interesting in Hildesheim.
(Don't forget that the Fagus Factory also are in the area, the same "Landkreis".)