It seems that Low End Mac has taken on something of a keyboard obsession in the last year or so. It started with a few articles about the Matias Tactile Pro keyboard (Has 'the Best Keyboard Apple Ever Made' Been Resurrected?), then moved to a few articles looking back at older keyboards, notably the Apple Extended, Extended II, and the Northgate OmniKey.
My laptop articles have often focused on the relative merits and/or weaknesses of laptop keyboards, including the good (MacBook, PowerBook, ThinkPad), the horrible (Dell), and everything in between. The one constant, however, is that the keyboard is the part of your computer that you touch the most, and, strangely, it's the part that most buyers pay the least amount of attention to.
It's not a matter of Mac vs. PC or how many function keys you want, but of build quality and switch type. There are many types of keyboard mechanisms, but all keyboards sold in the last 20 or so years use either an Alps Switch, a buckling spring, scissor, or soft dome to get their feel, along with a membrane switch to register the keypress.
Clearly the most important thing that any keyboard does is registers the letters that you type, but how it feels in that process can make the difference between fast and accurate typing and slow and sloppy gibberish generation.
After reading Charles W. Moore's columns for years, I know that he prefers keyboards with a soft touch. In his case, it's due to a medical condition, although he may very well have subjective reasons for that preference as well.
I prefer a heavy, clicky keyboard. Clearly, Mr. Moore and I probably won't find happiness typing on the same keyboard, though strangely two models are on both of our lists of the best keyboards ever made: the WallStreet PowerBook and the PowerBook 1400.
I like those two keyboards because of the precise mechanical feel and the distinct feel when the key bottoms. These are soft keyboards, but they're also made with high-quality scissor mechanisms that are precise and have no slop.
Slop equals typographical errors, and typographical errors equal wasted time and effort. A soft keyboard also influences how the typist's hands must rest (on or off the keys) and what sort of resistance is felt when entering a keypress.
Most of us can adapt quite easily to a soft or firm keyboard.
A ThinkPad's keyboard has a much longer key travel and much higher effort than the keys on a PowerBook 1400 or WallStreet. The feel is totally different, but it's also my absolute favorite laptop keyboard ever, with the MacBook a close second (short travel, but firm action).
Firm action may hurt the fingers of some typists, but I find it reduces fatigue as I can rest my fingers on the next key that I'll type rather than maintaining tension by holding my fingers above the keyboard.
Which brings me to my favorite keyboard, one that has seen upwards of ten computers (both PC and Mac, sometimes both with a KVM switch), 21 years, and millions of words. It is the famous IBM Model M keyboard, in my case one of the earliest PS/2 models made in late 1986.
My
Model M wasn't pretty, with all sorts of dust inside and the keys
covered in crud, but it worked great and is still the fastest and
most accurate keyboard that I've ever used. Over the holidays I
followed the care and feeding advice over at clickykeyboards.com, and now
my Model M looks shiny and new again.
So happy was I that I went back to clickykeyboards and ordered a brand-new, unopened 1995 Model M to use at the office, replacing a fairly new and quite nice Microsoft wireless keyboard.
With the Model M, I type faster than on other keyboards - much faster. My personal best on a laptop was 50 words per minute on my old 12" PowerBook. I've hit about the same speed on my various ThinkPads, MacBooks, and Toshibas, but the 12" PowerBook was, in my opinion, the fastest laptop keyboard.
I just took a typing test using my old Model M and hit 64 words per minute - and I had fewer typos in the process. There's just something right about the design; I really can't describe it other than saying that my finger always presses hard enough and never too hard on a Model M - are two of the many reasons for typos on lesser keyboards.
Of course you still have to hit the right key, but even that seems easier on this most magical of keyboards. The new one I just bought cost almost $70 for something made well over a decade ago, and I consider it a bargain.
What
makes the IBM Model M so good? It's all in the spring - buckling
springs, to be precise. A buckling spring is a mechanism that
carries tension until enough force is applied to "buckle" the
spring, at which point it collapses and the key can travel down,
producing an audible click when it does.
What makes these keyboards so sound so distinctive (and so loud) is that the spring makes another distinct click when tension is release and the spring pops back into its original shape. In effect, you get two fairly loud clicks every time a key is pressed, making you sound twice as fast as you really are - not to mention annoying anyone in a nearby cubicle.
So noisy are these that IBM had to offer a "quiet" model (no buckling spring) for libraries and such.
Of course, while noisy and intrusive to your neighbors, there's one very good reason why the buckling spring keyboard remained in production for so many years and why it's something of a specialty item today. Those switches are very expensive compared to the cheap rubber domes in use today, and it's those switches that give this keyboard its legendary feel (and make it too expensive for this age of made-in-China mass-production).
You can still buy a brand-new Model M, and not only unsold old ones like mine, but a brand-new current production model. Unicomp still makes new Model Ms, only they call it a customizer. This is your only option if you want Windows keys (a huge convenience for use on a Mac) and native USB support. IBM and later Lexmark Model M keyboards all end in either a PS/2 connector, which can be adapted to USB, or the even older AT connector, which can also be adapted but is more difficult to deal with. Many of the old keyboards also were made for point-of-sale terminals and cannot, to my knowledge, be used on a modern computer of any platform.
Still, whether you get a new one from Unicomp or a used or unsold IBM, it's definitely worth the effort if you like a firm keypress. Unicomp offers a wide variety of styles, including colored (including black) keyboards; keyboards with built-in trackballs, pointing sticks or both; and your choice of USB or PS/2 and Windows keys or no Windows keys.
A plain black one with USB and Windows keys will be the best fit for most Mac and PC users these days.
Are there other great keyboards out there? Clearly, the Northgate and Apple 'boards mentioned in previous articles all appear worthy of consideration, and by the sound of it so does the Matias Tactile Pro.
I used to use an Apple Extended Keyboard II back in the day and remember it fondly. In fact, it was the only keyboard other than my old IBM Model M that I've ever hooked up to one of my desktop computers. I prefer the feel (but not the sound) of the Model M to the Extended II, but both are clearly high quality keyboards with excellent feel and very fast action.
It really is a sad thing to look at the keyboards that come with most computers these days. Whether you buy the cheapest $200 eMachines or the fanciest, highest spec Mac Pro, you're getting a plastic keyboard of dubious quality. Apple's keyboards are crumb magnets, and most PC keyboards are so flimsy that they won't support the weight of those crumbs. An old Model M, Extended II, or OmniKey may be just what your Mac or PC needs.
One thing is certain: If you generate a lot of text, you owe it yourself to get a decent keyboard.
When I took a three day trip last month and had a writing
project due, I brought my Model M in my luggage. My current Toshiba
Portegé has a comparatively good keyboard for a laptop -
good enough that I've used it to generate copious prose - but given
the choice, I'll take my 20-year-old IBM Model M any day of the
week. 
Editor's note: I'm a huge fan of the discontinued Logitech Cordless Elite Duo, which is far better than any recent Apple keyboard and has great drivers for OS X. I simply can't work with any Apple keyboard made in the past several years - they're just too mushy. dk