My take on this issue is that there's nothing new about common core and that most of the complaints being made pertain more to NCLB than to Common Core. It seems like a delayed reaction and the complainers just seem a little confused and misinformed. I think the most fundamental mistake being made is confusing curriculum with testing. Mandated, standardized tests are being aligned to fit Common Core, but the tests are not Common Core. Common Core is simiply a list of teaching objectives. In fact, those objectives are listed in two PDFs available here:
http://www.cde.ca.gov/re/cc/Nationwide standardization of curricular goals is not a bad thing as it allows for consistency of the educational experience for those who move from one state to another. Continuity is a good thing for those who must relocate. On top of that the standards listed in the Common Core are just plain and simple common sense things that you'd want all kids to learn regardless of who they are or what they plan to do with their lives.
I agree that placing too much emphasis on test scores is a bad thing, but we've had mandated tests for several decades. The importance of these tests has increased due to politicians talking about accountability and some weird idea that all children learn with equal ease and that somehow failure of children to learn is the fault of the teachers and of the schools. Almost any teacher can be transformed from an "effective" teacher to one deemed ineffective (or vice versa) simply by plugging them into a different community. Test scores are a reflection on the community, not on the teaching staff.