I never looked that closely at panels while over there. Are most neutral busbar terminals the type where the end of the screw clamps down onto the wire inserted in a hole, or do they have flat plates clamped down on the wire by the screw like most receptacles?
I don't have a problem with the common neutral/ground busbar, but I'm not sure I like the idea of using the same screw for a branch cct. N & G. If the N & G stay connected firmly together (twisted maybe?) but the connection to the bar works loose while an appliance is connected the "ground" on that cct. is going to float right up to 120V.