I got one for my dober. Are they anymore effective than a normal dog coat? I would say not. Less bulky, yes. I like the adjustability at the front but the leg straps on him were a bit snug and without them it's not very 'stable'. He's a cold dog at the best of times so if he's teeth chattery cold I now just use it as a layer over an equafleece or his 'witney' rug. They may be 'warmer' on a longer coated breed. I personally wouldn't spend the money again but have heard good reviews (which is why I got one) and horses for courses. Perhaps suitable for warming up at agility I.e. Exercising/practicing but keeping them warm standing about between runs I would say no.
I have a back brace thingy for me. It does seem to help, it definitely helps more than a normal back brace thingy would. How much of that is the placebo effect I guess I'll never know
I bought one for my GSP a couple of months ago. Myself and my agility trainer both noticed how much better he seemed in the colder months as I started running him in his Equafleece, so we figured it was because his muscles are warmer. So I bought him one which he wears in the morning before we go training at lunchtime and then he wears it for a couple of hours after. We think there is an improvement in him. I usually try and have him wear it now for a few hours a day.
They aren't meant to actually warm your dog up heat wise, they work on the muscles.
I am going to buy a mesh coat for my 10 year old Border Collie that still competes at flyball and I've just semi-retired to allsorts/veterans at agility, a friend gave me a coat that they bought for their large min poodle that was too big for him, it is slightly too small for BC, she is a small Border Collie, but has been wearing it at the couple of flyball comps we have done this winter. I have a couple of pairs of back on track socks and I find they help with my arthritis and I got a fleece jumper from my parents for Christmas, that I have been wearing after a day at competition and haven't felt stiff the next day!