yeah, every time i took my kittens to the vet for their checkups, i'd be asked what i was feeding them. the vet always seemed quite pleased when i said iams.
remember, though, that you can't switch food cold-turkey. over a few days you should change over gradually - 3/4 old 1/4 new, 1/2 and 1/2, 1/4 old 3/4 new. more slowly if you think your cat will be sensitive to it.