I recently become a fan of Joe Bower's blog, "For the Love of Learning" where he spends a lot of time explaining why he despises grades and wants to abolish homework. He shares the reasons for his sentiment as well as many alternatives. You can read about his dislike of grades here and his dislike of homework here. He's also a fan of Alfie Kohn who has provided the foundation for many of his beliefs and in his Museum of Education post, he shares a collection of his poignant articles like grades provide little to no information for students to use in order to actually improve.
As I reflected upon my own experience as a learner I realized that my report card had summed up my whole year or entire college experience with a few computer-generated numbers or letters that made me easy to quantify for school report cards and district report cards and state report cards and maybe federal report cards, but they didn't really say much about who I was as a learner.
I then took a look at how many unschooling and homeschooling families report on student learning collected at askpauline.com at this link where you'll find samples like K's 3rd grade summary/log, A's 7th grade unschooling summary, and many more. When you read these ungraded reports of how children spent their year, you get such a deep insight into who these children are, what their passions are, and how they spent their year.
Compare that to typical report cards our students get today and you'll easily be able to tell who's got it right when looking at "The No Child Left Behind" accountability lead system of better ed = more tests and harder tests OR the Joe Bowers and Alfie Kohns of the world.