Mine go to sleep, but are never turned off.
They are all monitored by UPS's, which show actual power draw. When sleeping, they draw almost nil, when awake, they draw about 65 watts (laptop with 22" LCD attached). That's why I switched back to lappys exclusively -- my solar system can power them 24x7, along with the FIOS, router and switches.
I never use hibernate, because my machines are online all the time, and also have to be woken up for backup every night by my server. Hibernate doesn't play well with server side backups.