my understanding (someone correct me if im wrong) is that he at least claims something similar to what Shimraa said... that the basic story was written (i thought it was 9 movies) and he choose that middle section to tell. And yes, from what ive heard he didnt know if the movie would be successful and if he would be able to actually make IV and VI so he made IV so that it could stand alone. Hence the reason why when it was first released it didnt have the Episode IV A New Hope in the crawl. (this change I dont mind, though some people seem to, I like the fact that some of the LD->DVD transfers (EditDroid) have included both crawls because i think its neat to see that, but i do feel that this was part of his original plan for the OT, that is to have it as Episode IV)

as far as getting 'yelled at' by critics and the public, I say those critics and pubic that did the yelling dont know what their talking about and need to remove their heads from their anus. The LOTR books which PJ based the movies on didnt wrap up all nicely after each book. Its just like people that said he was trying to capitalize off the title 'The Two Towers'. someone should put people like that out of my misery.

but anyway, i digress.
Rarchy after reading your post Im second guessing what I said, I think it could/does work with the ending of TPM being 'happy' If you look at it from a not knowing the story in the OT point of view, as far as you know everything was made all better, Palpatine appears to be a good guy who is just trying to get the republic back on track and that is accomplished (for the most part) at the end. there are some hints of more to come from Qui-Gons funeral scene and Yoda/Mace's convo. I guess I thought the celebration parade was just a bit too much

-Darth Simon