If your dog is a long haired breed it probably would not be noticable. I however have a Dobe, so it will stick out like....well um....dogs balls I've ordered one (it's not here yet). My daughter said she wouldn't come out walking with me if I was going to use it, not because she thinks it's cruel, she just thinks people will be ignorant and possibly abusive, so I came up with the idea of the bandana or a cover for the collar. Heck I can't sew, I'm hopeless, but I figured how hard could it be to make a cover for it Some iron on velcro (easy), and if I wanted to be really neat and tidy, I could just do a simple stitch around the fabric ;)
However..........maybe Kelpie would like to do a test one for me, fancy a trip to Tassi