Marko has done a couple of posts on the IBM Model M keyboard, quite possibly the best PC hardware ever made.
IBM made some significant mistakes with the design of the original PC, but they got the keyboard right. This was all the more impressive because many computers of the day had keyboards that were impossible to touch type on, like the membrane keyboard of the Atari 400, or the keyboards with remote-control style rubber keys on some others. To make matters worse, most of these keyboards were built in and could not be easily upgraded.
The original PC keyboard was further refined into the Model M--Same key feel, but with additional keys and a better layout.
When a low cost IBM PC was $2500 and even cheap keyboards weren't all that cheap, this made sense. When computers are down to $300, spending 1/4 of the cost on a keyboard doesn't. This is reflected in the keyboards for most PC's getting cheaper and cheaper
IBM also had the best laptop keyboards I've ever used on the mid 90s Thinkpads--A similar feel, with a shorter stroke. One of the dumbest purchase choices I've made was when I bought a new low-end Toshiba laptop instead of the clearance IBM of marginally lower spec.
New type M's are around $70 shipped from pckeyboards.com This sounds outrageous for a keyboard, until you figure the per-year cost. I retired my 1988 keyboard that was still in perfect working order to replace it with a 1990 M2, the slightly smaller, lighter and less rugged version. I'm a little lucky that my USB port will drive this keyboard, some of them draw too much current for some USB ports.
If you need peace and quiet, the Type M isn't for you--they make a quite loud click on both the press and release. On the other hand, when someone hears you typing, they think you are twice as fast as you really are...