The one I put on mine has been working fine. Notice that the old non-mercedes one had stamped vanes and the new Gates one has is cast.
When I worked as a diesel mechanic and on my own vehicles I have insalled water pumps with cast impellers, stamped impellers and even plastic impellers and the all worked right except one. I had one Water Pump where when the coolant got hot the cast Impeller expanded and did not turn because it was not gripping the shaft. When it cooled it gripped the shaft.
I have also had rebuilt water pumps for Cars that leaked but no issues other then the one I mentioned with impellers.
Water Pump With Sheet Metal Impeller Vanes 617.952