All right, I did some poking around... both in the game and in looking through the GF3 data files. Unfortunately, the script files that provide such clear information on items, creatures, and attack types are almost useless for the enhancements, which must be handled separately.
On armor:
- As far as I can tell all effects -are- cumulative.
- 5 of the enhancements add +5% to one resist stat -- bless adds to armor, "resist magic" adds to electric, and the elemental ones add to fire/ice/acid.
- "Resist effects" adds +5% to hostile effect resistance, i.e., all 7 resist stats.
- Spiked armor takes effect every time you are hit, and damages the attacker. The damage varies. With one piece of spiked armor it's usually around 50% of attack damage. With two pieces, I *think* the range of damage increases, but I'm not sure, and I don't yet have 3 of the enhancement.
- "Bonus to-hit" presumably gives you a +5% bonus, but I haven't tested it.
- I can't tell if "avoid blows" does anything at all.
- As far as I can tell, "Regeneration" does NOTHING on armor. Is this a bug or have I missed something?
On weapons:
- "Hits faster" does nothing that I can see.
- I think blessing increases chance to hit by 5%.
- "Stronger" (golden crystal) increases base weapon damage by some factor. I suspect it adds an extra die to the base damage. This usually increases damage by less than the effects below, but the advantage is that it takes effect on every single hit, plus it also affects Quick Action hits.
- The other 7 enhancements all trigger on successful hits, NOT including Quick Action hits. They will not trigger every time - I'm not sure what affects this.
- Fire and ice brands and the spike will do extra damage (usually around 5-15) of the appropriate type. Spike is physical damage, so it doesn't get resisted, and is probably better.
- "Regeneration" ONLY when on your weapon, not armor, will heal you for a small amount of damage (around 5-20). I haven't tested to see if the life drain doesn't work on undead.
- Acid brand, cursing and slowing add the appropriate status effect at a relatively mild level.
- These effects are all handled DIFFERENTLY from native weapon (or creature) attack abilities. (Thus the Stunning Blade, if given the slowing enhancement, can actually slow the same enemy three times in one attack (native ability and enhancement off first swing plus native ability off Quick Action).)