I would be extremely cautious about #1 (replacing PNGs with CSS3 transforms and drop shadows). Your page load time may decrease but your website performance will suffer. For example, when we swapped out CSS3 box-shadows for repeating PNGs with the same color gradients/transparency, the scrolling performance on our page increased dramatically. I would also say from a design perspective, the 2nd Book of Mormon browser-rendered transform looks significantly worse. The edges are not being anti-aliased.
