I don't really mind laying off the religion and politics, particularly since maybe the point of this thread got a little off track, but that's the way conversations go. Just to be clear, at no point was I ever offended by anything that was said nor did I mean to offend anyone (my apologies to any quasi-facists out there!) with my comments.
The discussion about nationalism was as Chris explained, only to clarify the term. Despite its academic use, we have to recognize how the term is widely interpreted. For example, if I said I was part of a Japanese kenjutsu group with a nationalist agenda and dedicated to preservation of the Emperor system, I hope some eyebrows would be raised and that I would be questioned about what that entailed. To be sure, any such group would probably not have me as a member anyway!
Also, the talk about religion was prompted by Dennis asking about why the character for "holy" is used in Uehara's dojo name. It's a difficult question, because I think there is possibly some historical link to Okinawan religious practices through the ceremonial role of the Ryukyu kings, but there is no religious proselytization going on in the Motobu Udundi organization--there's not even a shinden in our dojo. Anyone of any race and faith I think would feel welcome.
Dennis and Chris are absolutely right that the differences between Udundi and other arts extend to more than just technique. Actually, as people have mentioned elsewhere, there is only so much you can do with a fist and a leg and an opponent's body, so most techniques in Udundi will be familiar to people who have studied other arts. The hardest technical part is mastering the fundamental difference in the way bodyweight is used. It's not at all easy, and as other commentators have mentioned, can be especially difficult for karate-ka who have been taught to drop their center of gravity for stability and "wind up" for strikes. It's also very hard on one's feet and ankles in the beginning!
Let me just paraphrase from the preface to Uehara sensei's book as to what he says udundi is: at the base, a bare-handed system of taijutsu based on punches and kicks PLUS kenjutsu, iaijutsu, training in various weapons, horsemanship (would be cool to learn!), ropework, etiquette, healing, and their application in daily life and on the battlefield. He also spends a lot of time in his book explaining how the ethical component of udundi is absolutely central, not something that was tacked on.
Uehara sensei is very explicit in saying that you cannot study udundi just in its technical aspects, and my sensei have all been very clear that udundi techniques alone are not always going to be enough to overcome an opponent, but the cultivation of preparedness, a certain mentality regarding oneself and others, and energy conservation among other things just might give one the necessary edge. Why else would I get a 15 minute lecture on why NOT to bow every single time I enter and exit the dojo, or how to pick up items such as weapons while still remaining alert and able to respond quickly (NOT from seiza!) I've had lessons where the time spent on these things and was longer than on any kata.
As for kata, anyone who is looking in udundi to study the ancient kata of the kings is going to be disappointed. Udundi maintains a strong tradition of individualized instruction, so any kata done at any time are simply for the education of the student--I'm sure that's the tradition Uehara sensei learned and maintained. That's why the kata we do now are just called 1, 2, 3, 4 and 5. Plus we have recently been doing two new ones introduced by our shihan because he thinks we are too slow. They're just called "punch kata" and "kick kata". Whether today's kata will be the same in 20 years is really an open question. The importance of this instructional philosophy will probably keep udundi a rather minor art and make the production of any kind of udundi "manual" impossible--probably as it should be.
Oh, and please don't anyone take me as an authority on any of the above! I am only reporting my perceptions on a small fraction of what I am being taught in order to clarify some really big misperceptions of udundi that have been around for far too long. I don't have as much skill or experience as many of the people on this forum, but I will gladly try to give my perspective from inside an udundi dojo for anyone who has any questions.