I think that they are very good alternatives to practice cheaply. Just for the record, your local gunshop can most likely offer you more options than the big boxes and at a somewhat reasonable price. For a rifle I like the Benjamin pnuematics and the fun Crosman 1077 CO-2 repeater. The Walther replicas are a good option for pistol practice. Even Airsoft will work and there is a Japanese World Champion that can only practice with one in his home country. He is often on Shooting USA during the Bianchi, IPSC and other matches but I cannot think of his name at the moment.
As an RCBS owner I choose not to participate in ammo shortages.