Many times we have chosen to take some of the rules and chuck the rest. I think the ability to do this speaks volumes of the quality and flexibility of the AD&D game system. Sure there are some holes in the game but that is to be expected of any game.
One case of this is the Players Option rules that came out in '96. There were a variety of changes in that text that were interesting and useful but we all agreed at the time that we did not want to buy a new book nor did we want to change the way we were playing the game. However, we all took notice of the addition of a set of sub-categories for each attribute score and decided that this was something that we wanted to adopt with or without the new book.
As a GM, there have been many times when I wanted to have my players roll willpower or reason checks. At times I found it difficult to reconcile the idea that the closest thing I had to willpower was wisdom. It just seemed that the two attributes were not close enough to make the roll sensible.
As a result we have adopted the new attribute sub-categories so that the GM has a wider range of options for ability and skill checks. We assign attributes to specific skills or non-weapon proficiencies on a case by case basis. You will find these categories built into our character sheets.
If you are not familiar with the Players Option text you may be wondering how you go about generating these scores. It's really very simple. The secondary attributes are based on your primary attribute scores and that means no extra rolling! We take the primary attribute score and repeat it for each of the secondary attributes. Once you have done this you can move a score up a point by bringing down the opposing score by a point.
*In our game system we allow players to modify the scores by a maximum of 3 points up or down and a secondary attribute score may NEVER exceed 18.