My vet has been telling people not to use pine either. I think he's referring to the stuff Wal Mart sells that is air dried. It has a very strong pine smell, and is not good for small caged animals either. Can cause respiratory problems I've been told.
I use kiln dried pine, and/or these new Woody Pet pellets.
The problem I find with the woody pellets is the chins roll on them, like that are roller blading.
They are great for odors, and sure make a difference with the gp.
I've used the aspen too, but it's expensive here.