I've tried it in a couple of tanks and, like Lisa, found it's a big problem if you get any into the water column.
I know someone with a 600L tank that's 50cm or so deep, he's got a 3-4cm cap of gravel over it and doesn't do much replanting. It's fine for him and the plants go well. With a shallower tank and/or less of a cap, it only needs one slip during a big water change or a bit of replanting and you've got ugly brown peat dust all over your plants. It's maddeningly hard to remove.
If you can avoid the dust problem, it's very economical. If you can't it's a pain.