I have one for every caliber I own. I think they are great, especially for the guns where you can't get a rod thru the breach, and have to clean thru the muzzle taking a chance of ruining your crown, which will ruin accuracy. :'(
For my shotguns, I use one of those rods that have lambs wool for the full length, with a bronze brush at the end. about three or four swabs thru there, and the barrel looks polished. I do keep a little gun oil on the wool to pick up the residu, and lube at the same time. ;D