It's always interesting... The qualification part makes it feel more like an "official world cup". Even though Zakstunts has higher status, ISM is an important event. I like the idea of racing on several tracks simultaneously, too.
To some degree, I think it is true that two IMSA cars out of three is too much. More variation could have been achieved by using Indy or Ferrari, or, if power gear was out of the question, Countach.