I just upgraded to MacTeX 2010 and had some trouble with previously installed type files in my private tree. Using MacTeX 2009 everything was installed appropriately in my local tree (~/Library/texmf) as well as the privately generated ~/.texlive2009 (cf the TeX Live 2010 documentation). I thought all I would need to do is rename the second directory to ~/.texlive2010, and keep the texmf in the library the same. This, however didn't work. 

I took the long way and reinstalled Minion Pro (easy with my script) as well as a few other local fonts. (With a detour through subversion hell: move, recursively delete .svn files, revert to old version, move back, commit) This then generated a new folder: ~/Library/texlive/2010 which seems to be the new home for privately generated files (although this doesn't seem to be documented for either the TeX Live or MacTeX). 

On further investigation it seems that the ~/Library/texlive/2010 directory is now where map files as well as local font files go:

kpsewhich pdftex.map returned ~/Library/texlive/2010/texmf-var/fonts/map/pdftex/updmap/pdftex.map

Almost all of this digging was done very cursorily, but since I didn't see any documentation (other than some for MkIV ConTeXt) I wanted to get this out here. What's not clear is if .texlive2010 has any purpose for MacTeX 2010.