While it looks like there is a bug, I have not seen it on my game and I have tested it a lot wiht the Xbox 360 controller.
I did have problems when I used a clone Xbox 360 controller under WinXP. It was very flaky and would not work at all on one of the WinXP machines, until I switched to an Official Xbox 360 controller. It now is rock solid and plays perfectly.
So whether I just had a bad clone controller or MS made sure theirs works better I can't say. But the problem only occurred while testing it on 2 WinXP machines. Vista and WIn 7 were fine.