I've been having a loft clear-out today (before you all gasp, don't worry, the Model M is safe) and I came across the Model M (1391406). I haven't used that board in 4 years but I did use a Unicomp Customizer 105 until 2 years ago.
Even after all this time, I plugged it in and my typing was so accurate. I usually take a while to adjust to a different keyboard such as from my Cherry G80-3000 to say a laptop keyboard or a Dell or Cymotion rubber dome, but there is none of that with the IBM. You could argue that both are "proper" keyboards so very alike unlike the rubber domes (the Cymotion is an odd board to adjust to using) and scissor switches, which is true, but that doesn't explain why my typing is more accurate on a keyboard that I haven't used for 2 years compared to one that I've been using everyday for several months!
I suspect that it might be due to the lightness of the blue MX switches versus the buckling spring. Maybe I'm accidentally clipping keys when typing on the Cherry board but the resistance of the buckling spring is such that these brushes of the keys aren't triggering a key-press. But irrespective of that - surely that's good design? The buckling springs do feel like they require more effort to press, but my fingers don't feel tired and I'd say that they have a softer landing than the Cherry switches. Don't get me wrong, I love the Cherry switches but they do bottom out very easily and I think that you create more tired trying to avoid bottoming out.
Another thing I have noticed, the 1394106 sounds very metallic (mostly on the key return) whereas the Customizer 105 had none of that, just a click. Is there a difference in materials between the IBM and Unicomp boards? I don't care for metallic sounds, I prefer a plasticy sound, but you can just feel and hear the quality with the Model M. Every key produces exactly the same sound and feels exactly the same.
I'm seriously going to have to buy a USB Customizer but having seen the beige Model M again I think I might go for beige rather than the black one I had before.