I fed Merricks TurDuckChicken to my JRT for years with excellent results. I no longer have the JRT..

I tired to feed Merrrick for a short time to my new dog and was pretty happy with the Cowboy Cookout, but then tried the Wilderness Blend and had to give the bag away! The gas that my dog produced on that flavor was shocking! eeww.
I haven't given Merricks another try...just because I find there are so many brands out there.
I like the company and generally think the food is very good.

If your dog is enjoying the food and not having any loose stool or gas, then I'd say it's working for your dog and stick with it!