Apple has been able to do "clever" things while asleep, like waking up the wifi chipset periodically to check for email / messages / notifications / updates, so that when you wake up, everything magically feels ready to go instead of feeling like you just woke up from 1984 and have reams of crap to download.

But this only works well because Apple does their own firmware for most of the machine, and seems to do a reasonably good job, despite a few issues. They're careful about only doing things that aren't going to obliterate the battery in a way that would be surprising.

Microsoft is jealous of this functionality and knows they want something like that for Windows. They also know they need to cater to the lowest common denominator with system builders, so they asked Intel to put this kind of capability into their platforms, and to explicitly disable the old modes, so that system builders wouldn't be able to drag their feet. The result is that they've all switched, but the outcomes are generally poor and high variance. Sometimes they're passably okay within Windows, but not always. It'll probably get better, but for now things are crap, especially on Linux.