I switched Humphrey to raw when he was about 7 months at the suggestion of my groomer and also my trainer because his coat was thin and dull. The groomer reckoned I'd see a difference in a fortnight, which I considered was rather optimistic, but she was right and after a month the difference was incredible. I believe the condition of the coat is, generally speaking, one of the indications of the condition of the dog so I was concerned that the food he'd been having previously was perhaps not aswell balanced as I thought. (I should add I live in Germany, so have no idea about the quality of any of the British brands).
Humphrey really enjoys his food and I feel I have more control about what goes in it and can also offer him a much wider variety. The ph values of the gastric juices are apparantly higher than those of kibble fed dogs, which decreases the likelyhood of infestation by worms or other parasites in the digestive system. I also understand that raw fed dogs are less likely to suffer allergies, food intolerance and other diseases. I've no idea how or if it has a direct influence over behaviour but can imagine a healthy happy dog has less issues than an unhealthy one. (Thats not that saying that kibble fed dogs are either unhealthy or unhappy but its often quite a difficult task to find the right one!).
If you're thinking of changing over however, I'd recommend you read up on it so you have some understanding of the concept as its not just a matter of giving just raw meat, the right balance is important. If you gooogle Ann Ridyard, you'll find some good information and there's also a facebook group called Raw Feeding UK which is very informative!