The DROID X 4.5.621 update is available now to Motorola Feedback Network members who signed up to participate in soak tests. As you know from the changelog we posted on Friday, this is a hefty bug fixer that should help stabilize your phone across the board. Head into Settings>About phone>System updates to pull it.
You will lose root after updating just like you will with almost any OTA update. We are hearing that OTA RootKeeper will work though. There is a good chance that the DROID 4 root method will work as well.
Cheers D and B!