So one of the benefits of the feat are as follows:
Aura Mastery (Use Magic Device 1 rank): Once per day, you can choose a single school of magic represented by one of your wondrous items’ auras; you treat your caster level as 1 higher when casting a single spell of that school. You can make this choice at any time during the day, but you must choose the item (and school) before casting the spell.
Does this mean that you add the bonus once per day or that you choose the spell that gets the bonus one per day, and get the bonus to all castings?
'before casting the spell' suggests to me that this is a one-time thing, but I'm not totally sure.
'before casting the spell' suggests to me that this is a one-time thing, but I'm not totally sure.
This is exactly the source of the confusion, since it can be read as "you don't need to choose at the beginning of the day, just don't cheese up and choose after you casted".
"a single spell" and "the spell" suggest that it's a one-time thing.
Since the feat gives you access to multiple tricks for which you qualify, not just this one thing, getting +1 CL to all castings of the spell would be unusually powerful as well, closer to being worth a feat on its own.
Thing is that "single spell" can refer to a single spell casting or to a single spell.
I also think the first interpretation makes more balancing sense, but I think it makes less rhetoric sense.