Since it's a free action to create or dismiss the shield, you can theoretically dismiss it at the beginning of your action, attack with your two handed weapon, and then create the shield again at the end of your action.
However, you would not be able to use the two handed weapon to make AoO's while you are using the shield. A weapon such as a bastard sword or waraxe would allow you to make one-handed AoO's while benefiting from the shield AC. Or you can use a weapon that's normally one-handed for you and just make two-handed attacks with it, and one-handed AoO's. Or you could use Monkey-Grip and just have a -2 on all your AoO's.
It really isn't all that great for spellcasters. It won't stack with mage armor or bracers of armor, since it grants an armor bonus like a normal shield.
For melee characters, it's not as effective as a normal shield, since even a +1 large shield provides a better AC.
It only has two real advantages over a normal shield:
1) Since it's force based it will protect against incorporeal attacks.
2) It gives fighters with a two-handed weapon +2 AC when they aren't attacking. But it's really only optimized for characters who can switch between one-handed and two-handed attacks.