As someone who graduated with a math minor and promptly forgot the vast majority of what he learned, something that really messed me up were gaps in my education.

For example, I took a graduate level course in the foundations of mathematics (proving natural numbers and arithmetic). I grasped the lectures, but one day I was completely stumped by a step in the proof where algebra was performed across an inequality.

I had never in my life seen algebra across an inequality! As an undergrad senior in a 500-level course.

I grew up moving a few times, and even within single schools I found the teachers weren't on the same page in terms of how math would be taught. For this alone, the Common Core sounds like a good idea to me.