In my opinion, the perfect keyboard has yet to be made. I envision a keyboard with the solid construction of an IBM Model F keyboard, the removable keycaps, LED faceplate and keycap lettering of the IBM Model M, the compatibility and much the layout of a Northgate Omnikey Ultra with a bit of the Apple Extended Keyboard.
The layout of the Model F, either the PC/XT or the AT version may be lacking for the 21st Century, but its build quality is second to none for PC keyboards. It uses buckling spring technology with stiff springs over a printed circuit board where the keyswitches are located. No membranes in these keyboards. They used steel and heavy duty plastic and weighed almost as much as the Model M, which used slightly lighter materials. Although rather annoying, every part of every key could be replaced. One lesser known feature of the Model F was that it did support N-key rollover, which the Model M does not.
Improvements of the Model M were keycaps that could be replaced without needing to replace key stems, making it much easier and quicker to rearrange the keyboard to the user's preference. The basic layout is standard today. The lettering IBM used on the keys and the LED panel is classic and professional. However, if you wanted a more stylish design, you can by replacing the keycaps. Replacing keycaps is easier than having to replace the keystem of the Model F. The cables, whether coiled or straight, were fairly heavy duty as these cables went. The SDL connector at the rear allowed you to change cables instead of using adapters, but today a lower cost connector could be used instead.
The Model M was criticized for putting the function keys above the keyboard instead of on the left side as on the PC/XT and AT keyboards. The Northgate Omnikey Ultra T put a set of function keys on the left side as well as on top. F1-F10 on the left side is in the same place as you would have found them on a PC/XT or AT keyboard, and F11-F12 are to the left of the Escape key, as they were added later. There was a switch to designate the top or the side rows of function keys are the primary and secondary function keys. With 24 function keys, any user should have enough keys for just about anything he or she wished to have a separate button.
Northgate's keyboards could emulate a wide variety of keyboards, including the PC/XT keyboard, the AT/Model M keyboard, the Tandy 1000, the Amstrad PCs, the ATT 6300, even the Amiga 2000 with dipswitches. My ideal keyboard would keep as much of this functionality as possible, using a dipswitch panel. A special driver should not be required for support in this day and age where cheap and powerful microcontrollers are readily available.
The Northgate Omnikey keyboards support N-key rollover, which the IBM Model M does not. They also have their keyswitches soldered onto a PCB. The IBM Model M uses a membrane sandwiched between the black plastic key housing frame and the PCB. The whole structure of the keyboard is held together by plastic rivets.
One thing about the Northgate and Apple keyboards is that they split the large + key on the numeric keypad into + and = (Northgate) and + and - (Apple). The Apple keyboard have added five keys, F16-F19 and an eject/power key on various keyboards. It also has F13-F15 where the Print Screen, Scroll Lock and Pause/Break keys are on an IBM keyboard. F13-F19 usually have no commonly defined role and there are plenty of keys in my ideal keyboard to accomodate them.
F16-F19 on an Apple keyboard occupy the area where the option LEDs are on an IBM Model M keyboard. Many keyboards have LEDs next to the Caps Lock, Num Lock and Scroll Lock keys. I am neutral to this. However, the keys that would be where the LED panel would be should be exactly the same size and use the same keystems as the rest of the keyboard.
The modern Windows 104-key keyboard includes the Windows keys, which seem to be a functional equivalent of the Apple Command keys. Occasionally, Windows keys can be helpful, but they can also very very annoying in their default usage. However, the menu key is a useless key that can be replicated with a right mouse button click or a shift F10. There is no reason for it to have a key as it really cuts down on the size of the spacebar. In my perfect keyboard, it does not exist on the spacebar row. There are plenty of function keys to assign it to.
Big L shaped enter keys, who needs them? I have never found them to be particularly helpful, and they cause the \ key to be put in odd places. Northgate shortened the right shift key, which is the only real flaw in its non-101 designs.