Do follow the instructions. I followed my previous habit of setting the old Camera Raw plugin aside, prior to installing the new, in case I wanted to revert. Apparently the installer refers to the existing plugin to decide what language settings to use - I ended up with all ACR buttons and menus displaying in an Asian character set.
Then after manually restoring the 5.3 version to its rightful place, I had to jump through some hoops before PS or Bridge could see it. Deleting prefs did nothing, nor did rebooting. I finally got it back to sanity by running cameraprofiles.mpkg from the 5.3 download. However, now I couldn't rerun the 5.4 installer, as it insisted 5.4 was already installed. I was finally able to get the 5.4 installer to work, only by rerunning the PS CS4 installer to reinstall CS4 (no need to uninstall.)
Will Canon PowerShot SX1 IS be supported in the final version?
I know quite a few that would really appreciate this!