I do this on pedi's recommendation. We tried 3 different formulas, Zantac, angling bed, smaller more frequent feedings, and now finally cereal in bottle each feeding.
He was instantly a different child with cereal. We use 1 teaspoon to 4 ounces of formula. So 1 and 1/2 teaspoons for 6 ounces. Spit up significantly reduced, no more screaming in pain.
I figure if pedi recommends it, it's benefits far outweigh its drawbacks.