We have been a cheerio free house for at least a year now. DD used to snack a bit on Daddy's GoLean Crunch (Kashi). Now, I will get a box of TJ's just the clusters with maple and pecan for her every now and then. I don't want DD snacking on cereal anyways. At least the granola type cereal seems less processed, (although it is very sugary.) It fills the cereal void and she won't eat as much of the stuff in one sitting. And, she would eat cheerios all day long. I try to keep snacks simple and fresh, fruit, nuts, cheese, nutrient dense. My kid might be a toddler anomaly, though, because she is not a snacker!
I remember reading something about how the process used to make all those "puff" cereals denatures or nullifies any nutrition that went in.