This blog entry talks about changing the boot order of Ubuntu and Windows. However, the same can be said if you multi-boot your computer using other operating systems with Linux.
One of the reasons to tweak your boot sequence is when you are testing other operating systems OR testing new kernels and/or kernel modules. I used to do this when I was experimenting with the latest and greatest kernels, without waiting for it to be included in the, and not reinstalling the entire OS.
So, the next time you have a multi-boot system, learn how to prioritize the proper kernel at boot time.