Lemon pepper makes a great coating for a different kind of steak au poivre. It gives the meat a little zing that plain black pepper does not. Also, it's usually broken up a little, so it's easier to get the pepper to a nice cracked consistency than it is whole peppercorns.
The pan sauce is also really good and different when you use lemon pepper with this -- or any -- recipe -- and the results are generally really good. It's always good to try something different and lemon pepper has worked for just about every recipe as a substitute for regular black pepper. I wouldn't use it in chili or beef stew, but for everything else, it's good.