The feat reads:
When you apply a metamagic feat other than Heighten Spell to that spell, the enhanced spell uses up a spell slot one level lower than normal.
I really believe it should read:
When you apply metamagic feats other than Heighten Spell to that spell, the enhanced spell uses up a spell slot one level lower than normal.
It's better grammar, and makes more sense gamewise. The way the first one reads, it implied only one metamagic feat can be applied to a spell at a time.