High level SoD's like Flesh to Stone are popular. Making your GSF add 4 to the DC of the spell is pretty wicked. I've not permitted Spell perfection yet in my games, but that's one of the most popular choices among those I know.
Yep, Flesh to Stone is nice, particulary with the the reach metamagic feat. I'm currently using Spell Perfection with Enervation with my wizard, a quickened enervation followed by a maximised one is a very nice combo ^^