I taught CK for four years. IMO it was VERY hands-on. Perhaps individual schools are just sticking to Hirsch's "What Your..." books but we were always encouraged to write interdisciplinary lesson plans and units that align with that content. Zane_Anthony, you can go onto coreknowledge.org to see more... and there are lesson plan links for teachers so you can see the sort of thing I am talking about. One neat thing about the CK foundation is that they hold a national convention each year - I attended in '04 and met teachers from all over the country; we shared lesson plans and teaching strategies. I've never gotten professional development like that in my public school job.
I loved CK in particular because I taught content that I personally wasn't exposed to until high school -- where else could I teach 5th graders about the Protestant Reformation?!

Believe it or not, kids CAN get this stuff at an early age - by coincidence I taught the Ref. when Pope John Paul II died. It was a great tie-in as I was able to show the kids live video of the events at the Vatican. I actually landed a high school job based on having taught some of this stuff. The little kids LOVED the challenging content, especially in social studies and literature. CK even has "watered down" versions of the classics like Don Quixote and a Midsummer Night's Dream for younger readers. I wish more schools would use CK.
The only downside I see is if your state has standardized tests in science and social studies. The state curriculum usually doesn't line up with CK from year to year; in my case I scrambled to cover more material than I CK had me doing so my kids could be ready. By 8th grade they cover all the same stuff, just in different sequence.