I have one from Northern Brewer on my aluminum kettle. Two years so far and no issues. I did purchase a replacement O-ring the last time I was in St Paul, however, just in case the O-ring eventually degrades with the heat.
I bought a step drill and made the hole myself, and I would do it again in a heart beat!
I can say putting the spigot on the kettle made transfering a ton easier! I would not have a kettle without one now that I know how easy it was to install and how well it works.