It's very simple... the new Bible has a more easy read in English. In reality, not much has changed. It's a matter of audience. Do you want a functional Bible that appeals to a wider audience? Or a technical Bible that stays closer to the original language? WTBTS seems to be trying to balance between the two, much like the NET, NIV and ESV. This revision gets them more toward the functional than the technical.
One thing they should not have done is added their biased commentaries. This is a big no-no in the translation community, but they seem to ignore that sort of thing.
I agree with whoever said they missed the running headings. They were a lot more useful than the outline at the beginning of each chapter. I undersand they got rid of it because it's a pain to update for each language. I get that. Makes sense. My take is: get rid of the outline, too. The outline contains paraphrased commentary, thus the term "governing body" got inserted in the outline in Acts.