As much as I agree that Obi Wan was kind of tossed aside in the writing of TPM I feel that Qui Gonn's character opened us up to a new kind of jedi we hadn't seen before. In the OT the only link we have to the Jedi are Obi Wan and Yoda. When moving back in time to TPM it is a good oppurtunity to show more aspects of the Jedi and Lucas took advantage of that oppurtunity. He showed us another aspect of the Jedi with the relationship between master and apprentice found in obi Wan and Qui Gon. If he had used the only two Jedi we had known of(Obi Wan and Yoda) things could have gotten a little played out. Qui Gonn added a new element and excitement to the story, he acted as a new character for us to get involved in. He brought a little refreshment to the story.
I must agree with Darth Daft in saying that Jinn was a crucial element in the film. His death and the style in which it occurred should definitely reveal somethimg to us in the future as to why Obi Wan vanished and Jinn was simply killed. Also I think that a new in depth character was needed to enrich the story. True I think Obi Wan got shafted on screen time and lines but his credit will be given in episode two and three. Jinn's character gave us a new look into the Jedi relationship of master and apprentice. A new character was needed to show this relationship. He also was needed to help show the changes ObiWan will undergo over time. Jinn in a sense helps develop Obi Wan's character to be a major part in the upcoming films.
we didnt need qui gon
although I had similar feelings of qui gon in when the movie first came out, after a while I was glad he was added to the story....come on...a hippy jedi...how cool is that!!! Liam Neisan played him perfectly and I can't imagine anyone else fitting that role better...
also, the midichlorian thing seemded to cheapen the mystical religon feel of the force (gave it a biological/gene feel), I think GL will show how it does not matter so much how geneticaly superior you are, it's how you master it and use your mind and ethical strength...
Obi wan is probobly (arguably) the best jedi ever, but he is not the genetic chosen one...Luke is probobly not as strong as anakin, but he has a stonger will to be good and loyal. The midichlorian thing may just be added to the story to demonstrate this idea...