When I discovered Alice, I thought my 9 year old son would absolutely love it. I downloaded all the models and everything for him. However, he got bored with Alice pretty quickly.
He likes to make games, so he uses graphical game making programs like the Games Factory and a few others. To some extent you learn programming in those types of applications. I would much rather he spend his time making games than spend all day playing them. At the very least he learns logical thinking and gets to be creative.
I'm not really sure why he doesn't like Alice. I suspect it is because most of what you do in Alice (as of about a year ago) is more like writing a story than writing an interactive game that gives the operator many choices. Although, I must admit the ease of getting 3D Graphics working is very cool.
So in answering your question more directly, it has been my anecdotal experience that it had an initial cool factor, but it wore off in less than a week for my son. If the person you want to get interested in computers is creative and likes computer games then maybe investing in something like The Games Factory or Multimedia Fusion from www.clickteam.com will generate an interest as they will be able to do a lot more in less time. It certainly has kept my son interested, since he was around 6. (P.S. I have absolutely no affiliation with clickteam, that just happens to be my son's favorite).