My son, Nigel, was gaining weight normally however he constantly spit up an hour or two after feedings. The Dr. would say "it's more of a laundry issue" (Thanks Doc)!!
Finally one of the Drs. rotating at my son's Ped office heard me through and gave us samples of the Alimentum Formula. Within 2 days my son changed!
We no longer have to hold him at arm's length, he's able to hold his formula down. While it's expensive - its definitely worth the price tag. He has been on this formula now for 5 months and we'll continue until he's a year.
FYI, many drugstores and supermarkets hold only a few on the shelves, therefore, it's best to stock up and buy 2/3 at a time if the formula works for you.
Good luck!