We bought this for our 6-month-old Whippet pup for separation anxiety. Despite having left him from day one and having built-up leaving him very gradually, he would still bark if left alone without our other dog and bark if left for longer than 45-mins with our other dog. He was only ever left for a maximum of 2-hours, but because the neighbour worked shifts, we felt like prisoners in our own home.
The Thundershirt has meant that we can now leave him for over 1.5-hours with our other dog without even a peep from him. We could probably leave him for longer, but have not yet needed to do so. He will now amuse himself with his stuffed Kong whilst we are away, whereas before he'd simply ignore it until we got home. He is far better when left alone without our other dog - he still sometimes barks, but does not howl constantly from the moment he's left until the moment we return, like he did before. We have found leaving a pair of socks with our scent on and the TV on also helps.
A surprising side-benefit of getting the Thundershirt is how much more focused and calm he is at his pre-agility and obedience classes.
He was not bothered about the fireworks the other night. He is still bothered by big lorries going past whilst out on a walk, so we haven't noticed a difference in helping with that (but it's not a big issue for him).
We notice a huge difference when he's wearing his Thundershirt around the house - he doesn't badger our other dog and is a lot calmer. For those people who have a hyper puppy and would like a natural way to calm their pup, then this is a great possibility. (Although avoiding dog food containing any kind of artificial additives would be the first thing to try.)
All in all a great product and we have just ordered our second Thundershirt, so that he has one to wash and one to wear.