Josh,

A wing definitely produces lift by creating lower pressure on the top than on the bottom. You can take this to the bank, whatever else you hear or read. Shape is not the only characteristic of the wing that helps to create the pressure difference. As has been pointed out, the lift depends on the angle of attack as well. Conceptually, you can think of a symmetric wing at a non-zero angle of attack as a non-symmetric wing. The air that goes above the wing 'sees' a different shape than air that goes below. This is because the angle of attack causes the flow to make the over or under decision at a point that is not on the center line ( causes the stagnation point to move, to use some fancy words ). Appealing to this conceptual view, you can see that the 'shape effect' is available to us on a symmetric wing as well.

banktoturn