At the office, I use an Apple Extended II keyboard. I use it hooked up via a Griffin iMate, with a LED Cinema Display and 13-inch MacBook Pro.
Built in 1995, my model is still in great shape, with very little discoloring and no damage. The sound it makes is deeper than newly-built mechanical switch-driven keyboards.
The main problem with using an older keyboard on OS X is the lack of media-specific function keys.
Thankfully, Keyboard Maestro is to the rescue. I have all the major keys mapped:
Keyboard Maestro can’t light up the backlit keyboard, but that isn’t an issue. Also, it has a tendency to adjust the brightness on the laptop, not the main display, but again, this isn’t a huge deal, as I don’t adjust the brightness on the Cinema Display very often.
You kids can have your fancy Das Keyboards and Tactile Pros, but my beige aircraft carrier will do me just fine for years to come.