I just spotted two bugs in the latest version (2022.1.0) of Isaac sim, may be you can fix them soon in the next release.
The first bug is the method get_applied_action() in the acticulation_controller.py. If you only send velocity command to the robot, like in your hello robot example, the applied_actions.joint_positions is None, so call this method it will throw AttributeError: ‘NoneType’ object has no attribute ‘joint_positions’.
The second bug is caused by the default unit is changed from cm to m. I use current_stage_meters_per_unit = 1, which is m, but the get_world_pose() in XFromPrim still returns the position in cm, I think.
And there are a lot of troubles due to the unit change, such as the model will be clipped even the viewport or camera is far from the mesh.