In order to make metamagic feats usefull I devised a simple rule to use them for my players. Seeing as Magicusers get shafted on feats and then the cost is way to high at times to use them.
The system is simple as a full round action a PC attempts to enhance one of their spells with a metamagic feat. They must make a spellcraft check to see if they succede.
DC= 10 + metamagic feat level addition x 5 + spell level.
example: Empowered Magic Missile = DC 21 10 + (5 x 2) +1
If they fail the spellcraft check then the spell fizzles out and is cast with no effect.
Out of combat a player may take 10 on the check but never 20.
With the new skill rules I believe that the base Dc can be increased to 15 + metamagic feat level addition x 5 + spell level
The players seem to like this and they have actually used Metamagic feats in combat.