At least for me, a Sugar-based was extremely beneficial as a child (12 or so years ago). My Sugar-based OLPC XO-1 introduced me to programming and Linux, and gave me a system to use for experimenting with my UNIX SVR5 and C++ books.

Sugar is mainly built for kids that never had access to a computer before a Sugar-based one (kids in developing countries; so I'm not the target audience either), so that might explain some of your complaints.