Hi WK,
I saw the first printed issue of PLOS. As you observed, the editorial board contains a group of bigwigs including a former editor for Nature Genetics. So in terms of personell running the show, it is no slouch. The articles were hard to distinguish in quality etc. from many other biology journals though none were as flashy, catchy, newsworthy as Nature or Science (not that this is a bad thing)..at least they had an article on elephants
Thus far, it does not seem to be so different from your standard journal other than how it finances itself. I think it is way to early to tell if it will have an impact.