Always on.
For a period of a couple of weeks, i was putting my PC into hibernate mode because my room became an oven with it on, but i once got an error and it said the hibernation data was corrupted. So it's been on since then. i really need to check the logs and see what happened, since hibernate's works so well. The time it takes to wake from hibernate with open apps is roughly the same time it takes to load XP normally, open the apps manually, and then reopen the documents in those apps. Not having to do all that was really convenient.