I always check the option to auto-ground the first part when creating an assembly (though this user option still becomes randomly unchecked). But depending on how the first part I place was modeled, the orientation selected by the program may not agree with what I wanted (i.e., part Front may not match Assembly Front).
It would be nice to be able to toggle thru all the possible principle plane orientations during (or after) placing the component while preserving the parts' grounded status. I may be missing a trick, but it appears the only way to re-do a grounded component now, is to un-ground, constrain, and re-ground and unconstrain. Being able to do the equivalent of Alt-Tab thru all the possible orientations would save some time. As an aside, I wonder if this issue is why some folks don't like the auto-ground option.