tzor said:
I am going to have to disagree completely. (I suppose we could always ask him.) While Gygax did use a d20 in both D&D and AD&D, he used a table driven system for those d20's as they were used in combat and saving throws. The result was both non linear (the best example is the large zone in the combat tables for a result of 20) and non uniform. Unlike d20, rolling one better on the dice did not have the same uniform effect for all classes.
Your objection (which, honestly, I'm not sure I even understand) seems tangential to my original point, which wasn't based on how the tables are structured but rather on the distribution of the die roll itself -- a 1d20 roll has a wide, flat distribution, and a +1 modifier will always increase your chance of success by 5%, no more, no less, as opposed to other rolls where a +1 might increase your chance of success by 16.67% (1d6), 10% (1d10), 1% (d%) or a different amount depending on what your target is (any roll of 2 or more dice -- rolling 2d6 a +1 modifier makes a whole lot more difference if it changes your target from 8 to 7 than if it changes it from 12 to 11). D&D used the wide, flat d20 distribution for combat and saving throws, but used other rolls for surprise, initiative, finding secret doors, opening stuck doors (d6), bending bars, surviving a system shock, thieves' attempts to hide in shadows, move silently, and pick locks (d%), monster and NPC reactions (2d6), retainer loyalty (3d6), and so on. A +1 on initiative means more than a +1 to hit, a lot more than +1 to bend bars, and might mean more or might mean about the same as a +1 reaction (depending on the roll).
D20, by using the same rolls with the same modifiers for everything, changes the feel. A point of strength helps you to hit in combat just as much, no more and no less, than it does to open a stuck door or bend an iron bar, which happens to also be just as much as a point of Dex helps you on initiative, how much a point of Con helps you to survive a system shock, and how much a point of Charisma helps you to make a good impression on an NPC. Some people (a lot of people, almost certainly a large majority) seem to prefer this, because it's simpler, but it's never sat well with me, both because I like different probabilities and different adjustments for different activities, and because if I were to settle on a single probability distribution for everything it definitely wouldn't be 1d20.