Virtues of a good keyboard
Thresh's comments in BLACK
Kenn's comments in BLUE
Weight and Build Quality
The weight of a keyboard usually directly reflects on its quality. Good keyboards are heavy (usually due to more metal parts or heavy-duty plastic), whereas cheap keyboards are light. A quick way to tell whether a keyboard is really cheap is to pick up a keyboard by both ends and twist one end to the left, and the other to the right to test its torsional rigidity. Stay away from keyboards that bend and warp easily. Really good keyboards have a metal plate on the bottom of the keyboards to stabilize it and to keep it from moving while typing. (The Northgate Omnikey, IBM Lexmark, and CVT Avant Stellar keyboards all have metal plates and weigh 5lbs or more).
Hmm. I care about my keyboards, but that's a pretty interesting "test." So you're saying a "torsionally rigid" keyboard will have a better feel than a flexible one? Sounds kind of dubious to me. I'd have to say aside from the weight of the keyboard, it is important to look at the quality of the key caps. Some keycaps can be very cheap, and the printed letters rub off after a few months of use. In general, if the letters on the keycaps appear poorly applied, they probably are. Get one of these $5 deals and you may have a problem with anonymous keys later on. In fact, the earlier Microsoft Natural Keyboards had this problem - the lettering can be easily scratched off with your fingernails. The new ones (including the Elites) don't have this problem, and in general, keyboards with letters which are deeply injected or embedded on the keycaps are better.
Function Key Layout
One of the features I like the most are function keys on the left side of the keyboard rather than on the top, but fewer and fewer manufacturers make those nowadays. Having function keys on top can be a real pain to press, especially in the middle of a game! Even the best touch-typists have a hard time reaching for those keys in the heat of battle. Function keys on the left on the other hand are easy to press, and with just a little practice, it is quite easy to press the right keys when you need them. Unfortunately, not many keyboards have this layout, and the ones that do can cost quite a pretty penny! (Again, the old Northgate and new Avant Stellar models have function keys on the left and top. The Focus 9000 series used to have function keys on the left and top, but they aren't being made anymore).