Robsan
Yep, I use it. It adds more flavour than normal crystal as the rye is kinda "spicey". I used it to bump up the body on an 80/- entry to the SCB nationals in 2004 and won!
U prob won't get away with it in a light beer though (unless you want the "rye edge" to it). Could be useful for milds and porters through.
Aled