Mine are on Simpson's too. They are on the 80/20 and before that the grain free variety. We have been using Simpson's for over 18 months and have also received great service, our local pet store has just started selling it.
Both dogs twirl in excited circles when I put it out something my springer never did before.
I'm really glad that this food is taking off, I know and agree that the best food for your dog is the one that suits them, but if any one is in the market to change foods Simpson's have a wide range and would be worth giving a go.
http://www.simpsonspremium.com/So in short Geordietyke completely agree.