I feed natural instinct raw. I started to swap onto it about 10 months ago to try and alleviate one of my cat's allergies which seemed to be food related. It took quite a lot of trial and error to get it right, for instance they will only eat the lamb and chicken flavour, and it took a while to encourage them onto it, to work out the right portion size, and work out when to start defrosting the next portion, but I absolutely love it now and would thoroughly recommend it. We also spent a while mixing 'n' matching raw and some biscuits, but I soon found that it doesn't work and it really does need to be all or nothing, so we went for all.
I find that my cats are far less 'hungry' than previously, they don't constantly beg for food and don't bug me so early in the morning for their breakfast. I assume that's because it's all protein with no carbohydrate and they aren't therefore getting the hunger 'spikes' that you get with peaks and troughs in blood glucose with a carb laden food. Their coats have become much more glossy and soft, Milly's over grooming has completely stopped and an added benefit is that their poos are far firmer, smaller and don't really smell. The main down side is that there aren't all that many suppliers and you have to have enough freezer space. I bought a small chest freezer off ebay which I keep in an outbuilding, and I get our local supplier to bulk order it in for me when I'm getting low.
I'd thoroughly recommend it - the difference it has made to my cats is amazing and to cap it all, for such a high quality food, I reckon it's cheaper too.