[Micronet] Read this before you upgrade to Yosemite, if you use Homebrew or have added files to /usr
Jim Lindley has a post that is well worth reading if you use Homebrew/Brew or you have added other files to /usr (eg. /usr/local). Those files may make your upgrade take substantially longer. Mine took an extra three hours to copy my Homebrew and LaTeX files during the upgrade.
Faster Mac OS X 10.10 Yosemite Upgrades for Developers - Jim Lindley
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