If you hold positions, you need to consider the carrying charge. If you short term trade, unbundled is often cheaper, but you should look at the details contract by contract. It was originally designed for traders doing large volumes in a few contracts where they are willing to work out the effective costs including exchnage and reg fees.
Too bad that they changed the commission scheme (raised money). Actually where can I receive news regarding recent changes of their fee/commission plans? PS: I couldn't see they mention this on News at IB. So cunning!! http://www.interactivebrokers.com/en/general/about/newsIB.php?ib_entity=llc