Beyond the modules, SP2 included general performance optimizations. Users reported faster load times for large drawing sets and smoother navigation within the 3D modeling workspace. The patch also resolved minor annoyances, such as layer mapping errors that occurred when exporting drawings to DXF/DWG formats for use by fabricators.
Running ACSD 2015 without SP2 exposes you to data corruption risks (especially in bending schedules and large assemblies). autocad structural detailing 2015 service pack 2