When I rotate groups of objects I find that several (up to half) of the objects rotate in the opposite direction. This means I have to rotate all these objects individually. Is there any way around groups of objects spinning in opposite direction?

Unfortunately i don't believe theres an easier softer way, All objects have 3 rotations, x y and z. If say for example an objects x rotation is 180, then you rotate z, it will appear to rotate the opposite way, when actually it rotating the right way, just upside down. I've seen this problem when cut and pasting an interior, the tile sets rotate all together just fine, but some of the objects go all wonky because the additional axis rotations on them. But maybe someone has a solution i don't know about.

Nope, you said it all.