Obviously this is a response to Apple's back-to-school promotion, which they have run for several years. Last year that program got you exactly the same amount in credit ($199) towards any iPod when you bought any Apple laptop.
One advantage of the Apple program is that you could trade up and get a higher priced iPod touch model and still get the $199 in credit. It looks like the Microsoft program only gets you the slightly gimped 4GB Xbox with no trade-up. A lot of students might be bummed when they realize they need a $100 hard drive accessory to play a lot of the games.
Not a bad deal, but I wonder how many Xboxes will be given to students who were going to buy a laptop anyway. I think the Apple motivation is obvious: to get students to switch to Apple. Not sure if the formula works the same with Microsoft.