[Lalaith]

That's really interesting about the different marketing tactics. It was definitely marketed at children, here in Europe...lots of emphasis on the big polar bear and so on.
As for suitable ages for Pullman...I think seven/eight is a bit young, particularly for independent reading.
Not because it's too scary, but because Pullman is quite dense and literary in style - it's much heavier going than the Hobbit. I'd put it on a par with Lord of the Rings, at least.