I agree about the Model M. Mine was built in 1991, and I've had it since 2003.
I use it with my Mac, through a USB adapter. Interestingly, when I set the keyboard preferences to treat the Alt key as Command, it still treats the right Alt key as Option. I don't know if it's something specific to the Model M, or if it's something weird with my generic Holtek-based adapter. I use all 4 modifiers, so that was a bit of a bonus.
USB adapters are a lemon market. So far, I've tried buying 3 adapters. The Holtek one works well with keyboards, but not mice. The second one works well with mice but not keyboards. The third one doesn't work at all. They're all too cheap to bother returning. This is one way that Amazon, with its incredibly generous return policy, is increasing its retail dominance.