I think this sums it up pretty well. As other posters have mentioned, Windows works great until it doesn't, Mac does it well unless you replace some internal hardware with something other than their branded gear. O

OpenBSD hibernate, and power management in general, works great on Thinkpads but the developers specifically like and use them regulary, at least so I've heard.

So I don't think it's any one OS that works well or badly or better than another; it comes down to the combination of the OS and the hardware and the compatibility between the two...