10.0.6 was a major upgrade to FCPX, perhaps the largest since the application was introduced, and in number of enhancements larger even than 10.0.3 when multicam editing was reintroduced to the application in its improved form.
First, I would recommend that you not update while working on a project. No matter how tempting, always finish the project you’re working on before updating. If you’re working on a project that you think you may need to go back to at a later time, it would be advisable to, in addition to backing up your older version of the software, to also back up the appropriate Events and Projects for that version. Once you open the Events and Projects folder in the new version of FCP, they will be updated and will no longer open and be accessible in older versions.
The best way to do this, I think, is to assemble a copy of the FCP application together with copies of the FCP events and projects files, and then zip them up. Select all the items, right-click and select Compress X (number) Items. Do this before updating the software. Keep these together as an archive should something bad suddenly crop up with the new version.
10.0.6 also brings important changes in importing for DSLR shooters. For a short video on this click here.
One GOTCHA in 10.0.6 and later versions. There has been a subtle, but very important change to the Duplicate Project function. Previously if you duplicated a project to a different drive including referenced media, all the media would be copied to the other drive. This still works the same way IF the media is in the Original Media folder of the event. However, if there are only aliases in the Original Media folder, aliases that reference media in a different location, then only the aliases will get copied over, not the actual media. This is great for SAN users. Now, if you want to copy the media rather than just the aliases, after you have copied the event which only has the aliases, which will be orphaned when the drive is disconnected, you have to select the copied event and run the Organize Media function. This will replace the aliases with the actual media.
Click the start button to see all the new enhancements.