With all this great input I am getting a sense that memory from roll paper is still an issue even after using d-roller (or similar) to de-curl paper. The methods used above, are great for mitigating the curl but it seems that the curl will come back at some point. The key is to expect roll curl to return and to mount accordingly.
Not sure if curling is the issue. Once matted and framed most prints will stay pretty flat. I think the problem comes from larger ones that tend to show some warping depending on humidity levels. In the case of float mounting being discussed in this thread, this can be more problematic if you don't mount it since there is nothing against the print to keep it flat.
Personally I mount anything larger than about 20x24 to insure the print stays flat. In fact lately I have been getting away from matting altogether, and just go full bleed in a frame with a liner, with museum glass or acrylic between the liner and the frame so it's no where near the surface of the glass.
My latest quest is figuring out how Michael Fatali mounts his prints. I just visited his new gallery in Park City, Utah, and all of his images are face mounted to museum glass ... they really look stunning. You have to look really closely to realize they aren't just floating in space. He says they are all still cibachrome prints, so this may not be something that can be done with inkjet, but I really like the look.
