I've got one of the cheaper "copies", but it's a Craftsman, so it was made for SEARS by Dremel. Just about any one of the Dremel add ons will work on mine, including the ability to replace worn/damaged brushes. ( I've got one of the older styles though ) And mines still going strong after more than 5 years of service.
Just make sure that you do your homework. Mine was given to me as a gift, but if I had the choice, I would've gotten the Dremel just for the peace of mind.