I recently switched Abby and Daisy to NB and so far so good. Abby scratches less and the watery eyes have completely stopped! That's a big plus!
The bag we have now is Duck and Potatoe. I think next time we'll try the sweet potatoe and fish (is that right?)
I used to buy the big bag of Canidae, but it takes them so long to go through that big of a bag, that I worried about it getting stale. So with the smaller bags of NB, they can have more variety.
Like Brooke, I just switched A & D. No problems at all. Of course my girls seem to have an iron gut.
Good Luck!