Variant Rules: Successes and Failures

[kid america]

So I was looking through Unearthed Arcana and several other RPGs for some variant rules.

I was wondering who has had successes or failures, fun or misery with: 3d6 instead of d20, 2d10 instead of d20, Defense Checks, Injury system, Vitality and Wound Points, Reserve Points, and Massive Damage Thresholds

[kid america]

I should have prefaced this post with I was considering using these variant rules in Pathfinder and/or d20 Sci Fi game.