Our little girl was recently put on Alimentum and Zantac. We've been having stomach issues since she was born. We haven't had a doctor's appointment since the switch, but have one coming up on the 23rd (I believe). Therefore, I can't answer the question about weight. Just from looking at her, though, it appears that she has gained length and lost a little bit of her belly. We just went through a growth spurt, so that could be why.
She, as well, seems to have started "snacking" on the formula, except at night. She will suck her bottle dry then, but only takes between two and three ounces at a time during the day (usually). Personally, I think her problem is reflux and not a protein sensitivity. She was still fussy on the formula until she was prescribed the medicine. I'm going to talk to her doctor at the visit to see if we could try a different, less expensive, formula. If we have to pay for it, I don't mind. However, if it's just the medicine helping her then I want to switch to a cheaper formula.