Metamagic Feats and AoOs

[Xintas]

This is most likely a lack of knowledge on my part, as I tend to play roguish types, but how do metamagic feats affect AoOs?

Based on what it seems to be, a Silent, Still, Invisible spell would have no obvious or discernible sign of magic being cast until the effects began. Given that, it would seem that no AoO would be granted, but I do not see anything in the descriptions for the feats that seem to indicate that anyone threatening would be any less entitled.

I know this is rambling, but if I cast a spell with all that on it (or even just enough to make it so they could not know), does an attacker still get an AoO?

[Zanos]

Yes. None of those feats change the action you're taking from "casting a spell", so you still provoke.

If it makes you feel better, an AoO represents the moment you need to take to focus on something away from the battle, lowering your guard and allowing the enemy to make an attack. Spell-like abilities provoke attacks of opportunity despite not having verbal or somatic components for the same reason.

[Nightraiderx]

There's a skill trick in complete scoundrel that allows you to use bluff or sleight of hand in place of a concentration check when casting a spell, combine this with silent spell and it would definitely look like you weren't doing anything and things happening.

[Greenish]

Enemies don't get an attack of opportunity because they notice you're casting a spell and decide that it'd be a good time to attack you. They get an attack of opportunity because there's an opportunity to attack while you're focusing on casting a spell (or doing any of the other relevant activities) instead of not getting hit.

Quickened spells don't provoke, though.