I addition, you wear out your clutch bell if you have a steel spur. That takes a lot longer to replace than a spur does, and at $12 a pop. And while the bell is worn, it will wear the spur too, and soon you'll have a huge mess.

Plus, I really recommend that you run a light grease (not wd-40) on metal gears as well, for three reasons - first, without the grease it is very loud and annoying, second, it slows the wearing, and third, it prevents the electromagnetic interference that you can get from two metal gears (not likely, but possible).