Hi Ulrike et al,

> So in my opinion the current \mathbf-etc setup in unicode-math
> actually did the right thing and improved the standard
> \math-commands.

I’m replying out of order, but I’m still inclined to agree with you here :)
The big problem was not handling \mathit properly.

> I wouldn't like to loose this completly. If \mathbf
> pointed to a textfont then everyone who wants the real math symbols
> would have to replace \mathbf in their code by \symbf. And back
> again if he wants to use a text font.
>
> Wouldn't it be possible to have a "\usetextfontasmathbf..." command
> which disables the mapping to the math plane? So that one doesn't
> have to switch between \symbf and \mathbf depending on the font
> setup of a document?

It has been possible for a long time to select a text font for a math alphabet in unicode-math, but this feature was probably not documented very well.
If you try to select a particular unicode range such as \mathbfup and a font simply doesn’t have it (well, it only checks “A” I think), the remapping doesn’t occur and you get the ascii-range glyphs:

\documentclass{article}
\usepackage{fontspec}
\usepackage{unicode-math}
\setmainfont{texgyretermes-regular.otf}
\setmathfont[range=\mathbfup]{texgyreheros-bold.otf}
\begin{document}
text \textbf{bold}
$m+a+t+h \quad \mathbf{b+o+l+d}$
\end{document}

BUT this doesn’t work properly with \mathit, because unicode-math hasn’t distinguished “math alphabetic symbols” from “math text font”.

Cheers,
Will