although I don't use one, I don't think they are totally useless. good for 1 RM support...otherwise it's probably better to strengthen your back instead of using a belt if it is used as a crutch. IMHO
I bought mine for powerlifting almost 4 months ago and have used it exactly 1 time.. I definitly get stronger from training without it, and will save it for the lifting platform on meet day...