Minion Math with unicode-math

the release date for Minion Math 1.020 with MATH table support is October 2011 (as I still need to perform some tests before release).

In my tests so far Minion Math works (with fontspec and unicode-math) with LuaLaTeX and XeLaTeX, with slightly better results / less problems in LuaLaTeX. Optical sizes in math do work (with appropriate options for \setmathfont).

Minion Math does fully support 4 different weights. In the current setup, Bold Math (Regular and Italic) is taken from a bolder weight, so your example will need a few extra commands (\setmathrange) and will not work exactly, but almost "out of the box". The \fontsize commands should work (I will check that).

I suggest you contact the author(s) of this font family -- their website is http://www.typoma.com/en/fonts.html -- and ask them if they provide some code templates to help loading their fonts via the commands of the fontspec and/or unicode-math packages. I could imagine that the font-loading commands will depend importantly on whether you're going to get "just" the standard, i.e., "text"-size (ca 9-12 pts), optical-size font or one or both of the smaller optical-size fonts as well. Another consideration is whether you will have just the standard-size Minion Pro text (as opposed to math) font font or if you'll have several of the other optical-sized text fonts of this font family.

Given that the font-loading commands of Xe(La)TeX are rather different from those of LaTeX2e, I'm virtually certain though that commands such as fontsize{5}{6}\selectfont won't work. Instead, you'll probably have to use the AddFontsFeature feature (pun intended) of fontspec package to instruct TeX how to assign optical-size fonts to actual ranges of font sizes. E.g., you'll need to tell TeX that for anything less than or equal to 6 pts, you'd want to use the "Tiny" optical size (assuming, of course, that you have this particular font at hand).

Although this answer is rather late (!), I have recently used Minion Math with unicode-math, mainly with xetex (as luatex is a little slow). I have posted an example of an end document, which contains the unicode-math/fontspec template file within it, along with examples of the same document in other fonts, at http://empslocal.ex.ac.uk/people/staff/gv219/aofd/fonts/.

Update: April 2017: I have used minion-math with xetex for an entire book, now in press. See http://empslocal.ex.ac.uk/people/staff/gv219/aofd/

See also this question and answer: Fonts for Mathematics and Text