Former Lexmarker here; I bought a Unicomp keyboard to compliment my beastly Model M that I've used on every single computer I've owned. The Unicomp is good but I keep coming back to the IBM M. It's fun to have something physical that ties my childhood, job, and employment together like that. I like the fact that I can use a piece of electronic equipment on a daily basis and it still hasn't died yet.

As another commenter said, there are more modern keyboards available but the feel (and yes the nostalgia) of the M is yet to be beat in my mind for daily use. Although a few of the current ones come close...