Its a pretty nice find, thanks for the heads-up.
Its not an instant credit, its more of a rebate. Gets applied to your account after 8-12 weeks. Best to probably pay off all but @$100 of your initial purchase balance to avoid too much in finance charges.
Been looking for a good deal on the 360 or PS3, though I'm not sure which to get. Looks like the 20GB version and 60GB version are the same except for the front media readers, the built-in WiFi and the 40GB in HDD storage.