The main reason to use Minion is that it’s an awesome text face which ends up taking up a bit less space than other faces at a similar size without sacrificing readability (I used it for almost all my papers the last couple years of college, for example). As a display face, it’s not terribly exciting (especially since it doesn’t seem that the fonts designed for display size are included here; so these Minion fonts are intended for 10–12 pt. on paper).
IE9 shot would be interesting to see for comparison. Based on what IE people were saying over at Typophile forums, they made a targeted effort to dramatically improve the rendering quality of IE font rasterizer.
Firefox does really badly with Minion Pro at smaller sizes. Well, maybe someday.....