I used to like ascending AC a lot, then someone on these boards pointed out that determining if a hit was scored is (roughly) the same as the D20 formula.
Roll 1d20.
Add/subtract any bonuses/penalties due to your abilities and other modifiers
Add the AC of your target opponent
If the result is equal to or greater than your THAC0, it's a hit.
Now I use descending AC without complaint and convert far less because of it.
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I'm still torn where it concerns saves. Fortitude, Reflex, and Will are very simple, encompassing, and fit well onto characters sheets I design. Though I think a certain amount of "flavor" is lost when compared to things like "Dragon Breath."
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If I play D20 anymore, I'm actually just playing Microlite 20--which, barring a few minor aspects, I find very OD&D.

