I'll be the first to admit that the evolution of Android has lessened the need for rooting in several respects (screen captures, disable apps (not all devices, though), etc.).
One root task that I've posted about several times but I don't often hear other's mention is when you are rooted and install a busybox, you have utilities available to you to allow you to poke-around at the command-line level on your device.
I just hate not being able to use a lot of the (very useful) Unix commands (grep, find, tr, etc.) on my Android devices. I.e., it's not all about custom ROMs, kernels, and recoveries, overclocking/underclocking, boot animations, etc. for me (although I've done all of those things), but the freedom to poke-around at will.
To me, root = freedom and choice, while respecting the dangers and vulnerabilities that come with it