I installed OS X Mountain Lion today and have had a pretty good experience.

What I had to do:

  • Install the new OS
  • Install iMovie, iPhoto, and Pages updates via Mac App Store
  • Install Xcode 4.4 via Mac App Store
  • Install Xcode CLI tools (Xcode Preferences > Downloads > Command Line Tools)

Some Rubygems I use were built on libraries that had been updated (such as Nokogiri and libxml). I went ahead and removed all of my gems and re-installed them:

bundle show | awk '{print $2}' | xargs gem uninstall -aIx

gem pristine --all will work too.

Finally, Apple removed the Java runtime I had installed. Fireworks CS5 requires that. It offered to download it for me when I opened the app for the first time under Mountain Lion.

Other than the Java issue, I think most of these issue are to be expected when installing an operating system upgrade. Certainly much smoother than the upgrade from Snow Leopard to Lion.

EDIT Aug 12: I suppose I spoke too soon. I’ve been having an annoying issue where my laptop freezes trying to wake up from the screen saver. It seems to be this issue, but the energy saver fix doesn’t seem to fix it.