[mike: ~]$ uptime
18:19 up 9 days, 9:06, 2 users, load averages: 2.49 2.44 2.29
My mom's 4-year-old blueberry iBook is so stable that almost the only time she ever restarts is when there's an OS update. She regularly gets multi-month uptimes if she doesn't bother to use Software Update.
Whereas, my humanities teacher last year said that Windows XP was really stable for him- he only had to restart two or three times a week!