Ability Scores: No scores, just modifiers.

Attacks: No iterative attacks.  See Rounds.

Attacks of Opportunity: Basically, no.

Classes: 10 levels, cool stuff every level.

Metamagic:

Rounds: Free, Standard, and Move segments.  Allow extra attack on Move segments at a -5 penalty.  Allow extra spell on Move segment at...? penalty.

Skills: Award (base skill points) Class Skills automatically at level+3, +1 skill per 3 levels.  No restricted skills.  Cut down skill lists.

Spells: Cut down spell lists.