On a rogue/wizard I took silent, still, snd eschew materials.
A sorcerer in a game I ran took empower and silent spell.
I'm fond of but have not used empower, extend, or persistent for mages yet. Extend/persistent were just nasty on a cleric I played though.
I also really like the concept of quicken spell, but 4 levels is just to high a prioce to pay for me. So while I may take it for flavor, I'll rarely if ever use it.