I have a GSDXRetriever, and my parents had pure GSDs when I was growing up. Because he's a rescue, it's hard to know whether the traits are inherent to him/his breeding or due to his background. But:
-He always likes to have something in his mouth when he greets us -a ball, a toy, a leaflet from an old medicine packet, a toilet roll inner....anything will do.
-He's quite sensitive. He doesn't like it if part of the family goes out and the rest stay in -he wants to be with us all. Similarly, if I go for a rest because my head is bad, he'll lay at the top of the stairs so that he can keep an eye on me and an eye on my DH/children.
-He's smart, but not a smart as the pure GSDs were. He seems to follow instructions rather than working things out for himself Whereas the pure GSDs would work out how to open gates, doors, etc., Trigger is happy to just mooch around.
-He's fantastic with small animals. We have chickens and they can be let out to roam while we clean their pen. He just looks at them and either settles down at the end of the garden or goes inside. He's great with the cat, too.
-He's very neat and tidy. He won't get up on the sofa if there is something on there. He waits for you to clear him a space.