Wanted to give everybody an update on this. Picked up the car today and drove it back. All good news.

The transmission shifts much smoother. Before there was a noticeable jolt between second and third on both upshifts and downshifts. The downshifts are much smoother and I almost can't feel the upshifts now. Very pleased.

The transfer case fluid change also seemed to resolve the vibration/shudder that I was experiencing on tight turns. Smooth as butter now even on full lock turns under acceleration and uphill. This one is especially a relief, given all the stories of folks having to replace their whole transfer cases with similar symptoms.

I've had two other BMW indy shops tell me that I'm wasting my money changing the TC fluid and that I should just replace the whole Transfer Case, since it's a common failure on E70's. I am glad I didn't listen to that advice. TC fluid change being less than 10% of the cost of TC replacement should always be the first step in trying to resolve any drivetrain vibrations during turning (provided you don't have any specific codes indicating TC failure).

Thanks for the help everybody!