windows 8 boots up pretty darn fast. but i mostly use hibernation because it saves me the time to shut down all the apps that i keep on all the time. i am guessing it is all about RAM. 4GB is turning out to be bare minimum with windows 8.
Well, sleep and hybernate have been sort of combined and now called hybrid sleep.
Extract from Microsoft website:
Hybrid sleep is designed primarily for desktop computers. Hybrid sleep is a combination of sleep and hibernate—it puts any open documents and programs in memory and on your hard disk, and then puts your computer into a low-power state so that you can quickly resume your work. That way, if a power failure occurs, Windows can restore your work from your hard disk. When hybrid sleep is turned on, putting your computer into sleep automatically puts your computer into hybrid sleep. Hybrid sleep is typically turned on by default on desktop computers.