Ach, MG3..it´s a bit overrated, IMO. Sure, it´s rugged and reliable, but also heavy as shit and it´s difficult to shoot. Plus, the MG4 doesn´t completely replace it, the MG3 will still be used as a support MG on vehicles and Lafette mounts (another thing we kept from WW2).
EDIT: To stay on topic:
Sdkfz 251´s of "Großdeuthscland" on the Eastern Front: