It is still useful for some things.
If you reinstall windows xp and need special drivers (such as for a RAID-array), the only way to get them is putting them on a floppy and pressing whatever-key-it-is during the install. Of course, you can slipstream it, but that's more complicated. Stuff like that is still convenient to do with a floppy. Flashing BIOSes is often much easier to do with a floppy too.
Basically you can do without it, but it is really convenient in some special cases. If you have one, I'd say put it in. If you don't, don't bother getting one.