BluePhaze Xbox 360 and other Xinput controllers work, but It's bad excuse to ask the gamers buy new controllers are compatible with Xinput because a lot of users already have DirectInput controllers. Basically common USB gamepad is directinput controller, not Xinput controller. I hope you know what I mean.
alspal my USB gamepad has worked in older stable version of chrome, but new version stopped working now. (Chrome 32-33, also latest version of Firefox). in Cr.bug, about the reference, responsible claimed he dropped directinput gamepads due to instability.
Your link says everything about Raw Input for gamepads not directinput like Ashley said.
I know a problem, raw input is designed for keyboard and mouse, if someone has special mouse like has more than 5 buttons, it would conflict with gamepad, unfortunately D-pad doesn't work. I hope they should give 100% support to all gamepad buttons and avoid conflict (Gamepad Index and broken buttons) and we may implement extra to ask users to configure their gamepad in our wizard setup.