Best:
Streamlined weapon stats, critical threat ranges, and multipliers. Allows for very different weapons (club, rapier, light pick, greatsword) with very different "feels" and manages it without a lot of complication. Plus, weapons are very well balanced overall.
Worst:
"Memorization and Forgetting" of spells; just a dumb mechanic, klunky, and sure to be thrown out of the window pretty soon. Even a low-grade system of spell-casting points/manna points or whatever would be an improvement.
"Magic Missile" -- jeez, somebody please take that Holy Cow to the meat processing plant. Make it less good, right NOW.