Wow, I am in the minority here! This is the first year I put a creep feeder out since about 15 years ago. And I just put out the feeder about 2 weeks ago!
I have found my calves just don't eat creep well, ( I blame it on my high milking cows!! ;D). But my show calves, I wean about July (I'm late this year) and get them on feed then. The base mixture is gluten, corn, protein, then I add oats, molasses, soy hulls, etc as needed. Nothing special, but it is cheap (around 130 a ton now) and works well. I am not a big believer of all the "super show potions".
I calve in march through June....and my calves will weigh 550-650 in the first of Oct without creep. This year, I have several twins, several old "one more year" cows (that shouldn't have been kept one more year) and several first calf heifers so I did put out a creep feeder, and the calves are eating some. So I will be anxious to see what their weights will be....and how much more they bring, if any at all. Seems like around here, feeder calves bring the same PER HEAD regardless of weight (with a few exceptions).