Their food (and water!) consumption seems to be exponential - in the beginning, they are cute and fuzzy and seem to eat and poo a bit more, but man, at the end, I felt I was running a losing race to keep them fed and watered. I had a 15lb feeder and a 3 gallon waterer that I filled twice a day at the end. I almost swear that last week (I processed at 7 weeks) they doubled their feed consumption from the previous week.
On the other side, that same 15lb feeder keeps my layers (which numbered 2 more than the number of meaties), fed for a week+. They have a pool in the summer that keeps them watered, and a 5 gallon bucket that I have to dump each week in the winter to make sure they have fresh - they don't drink near as much -maybe a gallon a day. MUCH cleaner too.
I still think I'll do another batch of meaties this fall - the results were worth it to us. I had all roosters and I admit they did make me laugh when they would puff up and try to attack me....and then lay down from the effort.