Be careful about updating if you use third party Plug-ins
Contact the supplier first before you update to 10.0.4
Magic Bullet have tweeted the following:
“The FCPX 10.0.4 update breaks the preview functionality for Magic Bullet Looks & other plugins. Do NOT update. We’re looking into it.”
On the Apple Discussion forums, some users have noted the update shows choppy and sluggish performance, or hangs when previewing and playing project files.
Make sure you check with your Plug-in suppliers first.
My suggestion: If you have not updated yet – hold off for awhile