Is he still in middle school?
Theres a Lego Mindstorms compitition called First Lego League (see
www.usfirst.org) where kids (primarily middle school students) build robots that are full autonomous for a theme every novemeber. It's worth looking into if he likes the kit or if you want a test run first.
It's fun building, but imo, it's a little overpriced at $200. But it's a large kit and lots of fun if you keep it up. You can make some interesting things with it, I've seen vending machines, printers, scanners, maze bots, all kinds of things.
If he likes legos alot and is fairly smart, yes it's fun.
__________________
After a thousand years of oppression,
Let the berserks rise again,
Let the world hear these words once more:
"Save us, oh lord, from the wrath of the Norsemen"