Dennis, sorry it took so long to get back to you. Hessian, I disagree. The most glaring of the story changes that contradicts the series is secret-agent man Simon breaking River out of the Alliance lab. From the series we learn that Simon was contacted by some people that said they could get her out. While it isn't implicitly stated in the series, it is certainly implied that they delivered River to Simon already in the box. Why he felt the need to throw this story element away for the sake of that opening, I have no idea. He doesn't even attempt to address it in the commentary. While not as glaring an omission, Simon's conversation with Dr. Mathias also contradicts much of Simon's struggle to find out what it is they did to River.

Dennis - SERENITY didn't change any story elements from the basis of FIREFLY, but it did alter the FIREFLY universe fans know and love quite a bit.

What changed? The deaths of two main characters and the wrapping up of the main storyline of a third character (and by extension a fourth character's arc as well) - that pretty much constitutes a major change.

I really wanted to like this movie; and the first half was great.
But how could he possibly justify killing off two central characters if he was looking to get into the sequel business. The orginal crew of the Enterprise made 5 movies without a death (if you don't count Spock).
The second half of the movie had too many spaceships and not enough horses.

I think it's become fairly obvious that at one time Book was what The Operative was in "Serenity", and that The Operative will become what Book became. It fits the nature of the character as someone who has realized that he has sinned and must atone for his sins.

I agree that Serenity was a fine "ending". I think if they ever come back to the Verse, they are going to need to do some sort of prequel, which would work out well for Book, as we never really found out what his deal was.

Walmart has the Firefly DVD's for under 20 bucks today:

http://www.walmart.com/catalog/product.do?product_id=2350565&sourceid=28539535154120846828

What events did Serenity change from what was depicted in the Firefly series?

Serenity was a perfect ending for the Firefly series, and hopefully the beginning of a new moview series.

The best bit from the interview, to me anyway, is:

"we'll never make Firefly again, because that was a thing that existed and is now gone. And Serenity isn't Firefly"

It sure isn't. Firefly was one of the best TV shows I have ever watched. Serenity was a movie. I like to think of it as a fairly well done piece of alternate universe fanfiction. Clearly it can't be considered Firefly canon, what with the changing of events that were depicted in the series.