I guess I need to trick the FSM system when using my first name since it tends to block it. Anyway, the reader is encouraged to visit the IPMS website ( http://www.ipmsusa.org ), click on the link to the "National Contest Committee" and then use the link for "Rules".
When one judges at the IPMS national convention one attends a seminar for the judges. Questions can be answered and procedures can be clarified. Newbie judges, or OJTs, are always put on a team with more experienced National Judges. I've served as a judge in the Space and Sci Fi divison and as a team member, worked with some outstanding folks whose sole purpose is to provide fair and equitable judging of every entry on the table. During a national convention I have never been an ear-witness to a snarky comment by a judge or have I ever seen a judge act in an inappropriate manner.
There are two goals at a national convention. The first is to ensure fairness and equity in the application of the rules, and the second is to educate and train future judges for service at national conventions, regional conventions and local contests.
I have, unfortunately, seen and heard things at local contests and regionals that were not appropriate. The issue, here, isn't which set of rules is being applied, whether it be IPMS, AMPS, or other judging systems. The issue was that an individual judge either said or did something which violated the unspoken promise of the contest host that the judging would be fair and equitable. The problem lies with the individual judge and not with any particular set of rules. When I enter an IPMS national convention I am aware of the rules, just as I am when I enter an AMPS event. If I don't like the rules, or can't tolerate them then I should move on down the road. What I do not know as a contestant, but must take as a given is that the judges have been prepped through some sort of training seminar, that there is some supervision so that all judging teams perform their tasks fairly, and that the judging system has been fair to all entries.
Having said all that, the philosophy behind the IPMS rules, as seen on the website, have evolved over nearly 50 years of practice and procedure. IPMS rules guide the judges to look for evidence that the basic modeling skills are well in evidence before other factors come into play.
IPMS chapters are not required to use IPMS rules at their local shows so be sure to check out the websites for the host clubs, find the rules (almost every host club now has a web presence) and be sure you, as a participant, know what you're model is getting into.
An excellent way to view the judging process is from the inside, as one of the judges. You'll learn a great deal about what other builders do to make sure beautiful models by being able to get up close and personal with the model, and by joining in a conversation about the model with other judges.