I don't want to hothouse my children - when I say that I would want accelerated learning for my (eventual) kids, I mean accelerated in reference to the pace at normal schools, which I think often holds children back from their true potential. If kids are excited about a topic and allowed to delve into it deeply, they'll learn much faster than we could ever imagine. If the motivation is there, the learning is accelerated. And even if there isn't a strong motivation, when you provide children with personalized instruction, scaffolding them from where they are to the next step up, they will learn more quickly than when sitting in a group being taught the same material as everyone else.
I don't want to give my children free rein over everything - when I say that I would want to (mostly) unschool my (eventual) kids, I mean that I want my kids to recognize that learning happens all the time, everywhere we are. Education is not just what happens in a school - we are all students of life! Our curiosity can lead us to discover so many wonderful ideas and learn more than traditional schooling could ever teach us. For more unschooling philosophy, I really like ZenHabits's Beginner's Guide to Unschooling.
Some proponents of accelerated learning want their kids to learn multiple foreign languages, read at a college level, be ahead in math and science, and compete as a chess grand master - and they'll recommend overscheduling and pushing the children to achieve that. I'd say that you can raise a child to have those skills even as a (mostly) unschooling family - although maybe not the grand master part unless your child truly enjoys chess. It's all about the environment! If you want a child who speaks multiple languages, then live in another country or have a family member / caregiver speak another language in the household. If you want a child who is reading above their grade level, then read challenging material with them. If you want a child who loves math and science, then do fun experiments and play number games with them. And if you want a child who plays chess, then make playing chess a part of your family's routine. Parents are there to expose their children to the different aspects of life, to provide a staging ground for inspiration to strike. http://www.lifelearningmagazine.com/1204/parental_role_in_unschooling.htm