I am slowly reading "How to teach Mathematics" by Steven G. Krantz. This is a book with a lot of helpful advice about teaching Mathematics at the University level. In one part of the book, he discusses calculus reform. His remarks on this are very conservative, but not too negative.

I didn't really know what calculus reform is. I had heard of the "New Mathematics" movement, where students were taught about deep mathematical structures rather than multiplication tables. This was widely viewed as a disaster because the students were confused and they didn't see how the material related to any applications at all. I remember doing group theory at school. There were rules to fill in the table, but I doubt I knew why we were studying this topic.

Anyway calculus reform seems to be a different subject. The introduction of one strand of calculus reform was done at Harvard. Calculus reform is described by this web page.

One feature of the Harvard Consortium Calculus was an emphasis on application. Normally, this would be a good thing, but it can also confuse the students, because it requires additional knowledge that students may not have.

Interestingly the author of the above web page warns against using too many "concept questions".

See the paper for a more positive review of concept questions.