Stability can mean things other than not crashing. Nothing is more frustrating than having a runaway process doing lots of IO in Windows XP and bringing the system to its knees. In Linux 2.6 and later, I can sit there and have 5 compilations going on, with the disk grinding away, and the desktop is still smooth as silk.
Other than Kernel Panics, and Hardware failure the only time I have had to reboot a Linux box is for expediency (when it would take me longer to troubleshoot an important box than to give it a swift kick...