I've had my IBM Model M for over 10 years (even though it predates me) and it's been a staple in my computing. Nothing has been more of a staple and a constant in my life than that keyboard.
Unfortunately the left shift key pivot key became loose, and thus the left shift became unreliable. After looking at finding replacement parts, the one place that sells the part...also sells brand new Model M's. Killing two birds with one stone and I just ordered the Unicomp IBM Model M.
Coming from the 139041 model, I gained a Window key (Tux key as you can see) and opted for the larger spacebar.
Does it feel the same? Pretty much, I find the keys to be a bit more stiff but perhaps they need a breaking in period. USB is a great upgrade, but I've been functioning just fine with a PS/2 converter (blue dongle in the picture). I find it is slightly lighter in weight than the IBM Model M, I believe some parts were replaced with plastic versus metal, making this less lethal if war were to suddenly break out and you chose your keyboard as your first line of defence.
I will say that the buckling spring keyboards are not for everyone. This one is large and extremely loud. I have to mute myself on conference calls if I want to type without pissing everyone off on the call. Does it make me feel superior? Hell yeah it does.
Looking over my blog posts from ten years back, I posted about a IBM Model F I owned. Tragically, I lost it when moving and it hasn't seen since. At the time I purchased it for $48 USD in 2013 (back when USD and CAD were near parity). The same keyboard has now doubled in price, nevermind the shipping price. I'm kicking myself in the pants for losing that treasured piece of keyboard history.