I don't understand. It may not be as representative as the other forms, but it is just as predictive (from a rough survey of the various SDN threads). If you think the predictive value of all NBME's is poor, so be it. But then why even suggest taking one in that case? What is gained? Without the score prediction, knowing what the questions were like would only tell you how to study, not whether or not you needed to (or how much, the questions posed in this thread).
In any case, I only took forms 1 and 2. My step 1 had many "easy" questions that were as much like form 1 as 2... in fact, I had plenty of nutrition type questions that were very much like what I found on form 1.
I wouldn't suggest forgoing studying if you got a 190 on any of the NBME's, but I'd certainly feel comfortable about my chances of passing with a 225 on any form. But hey... they all cost the same amount, so take the "hard" one, whatever that means and whichever one that is. I just don't get the perpetuation of the myth that because it feels easy it has less predictive value. Not all questions on the USMLE are difficult.