iWork doesn't autosave, luckily... there's an app for that.

I recently switched to iWork and really liked until I left my computer on, unplugged, having it die and losing two days worth of work one day before the deadline. A quick google search turned up this: http://tristanchadwick.com/worksaver/

Install this app and it will auto save at an interval that you scan set. I don't know why this wasn't built into the software. I've gotta throw props to MicroSoft. Their auto save is a killer feature that should be a standard on all programs.