Hi
Yes, I'm using the shipping extension.
You can set the tax rates on shipping no problem, but If, for instance I am selling a child's coat which is zero rated tax, the shipping still charges tax because of the shipping tax setting.
If I set the shipping tax setting to zero and sell an adult jacket with IS taxable, no tax is charged on the shipping.
I'll have to look to see how other carts manage it and report back !