Not a replacement for things like Arduino, PIC, etc.as a replacement for embedded type of systems, like you would use an Arduino
As does having a smaller base of software libraries to choose from. There's much to be said for not having to reinvent the wheel or port things over from other platforms. One shouldn't ignore the wide availability of interface hardware and software available for some of the better established platforms.Of course that negates the $9 computer.
I'm not convinced that the Pi is going to meet the needs of an eight year old. Most have already been exposed to computers that can run software that you can buy off the shelf. Kids are even less patient than we are about instant gratification and computer kits are their own end as opposed to a practical tool to run interactive creativity tools and educational titles.Our soon to be 8 year old wants a computer. I've been thinking of getting a Pi anyway to run retro games and to stream Netflix/Hulu. I'll either give her my old desktop or retire it and build her a Pi as well. Saw that there's an Ubuntu distro for the Pi.