I used it on a layout I started a few years ago. It worked as advertised. The only complaint I have against it is that I couldn't figure out an easy way to remove the excess ballast. The layout was built on two 2'x4' boards, so I just took them outside and dumped the excess off. Another solution might have been to soak the ballast in matte medium and let it just glue into place, but I never tried that.
I used it on styrofoam, and it worked fine.
I've used the Woodland Scenics track foam on a couple of layouts now, and I like it, too. It's a whole lot cheaper than AMI road bed, but you actually have to glue down the track and ballast...