AoO on spell casting works for the party as much as it works against the party (since other spell casters don't pull AoO due to concentration/defensive casting).
I would imagine, now that I think about it, casting should provoke AoO; it makes the controller's and defender's jobs more important by creating a need to keep enemies away from certain other classes (and actually keeping them away from the caster rather than just making sure the enemy isn't focused on the caster).
Also, with movement becoming more important, it stands to reason a wizard will need to (and be able to) keep moving or keep pushing enemies away in order to be able to cast spells safely.
I would imagine, now that I think about it, casting should provoke AoO; it makes the controller's and defender's jobs more important by creating a need to keep enemies away from certain other classes (and actually keeping them away from the caster rather than just making sure the enemy isn't focused on the caster).
Also, with movement becoming more important, it stands to reason a wizard will need to (and be able to) keep moving or keep pushing enemies away in order to be able to cast spells safely.