According to Engadget, the update brings with it (besides Android 2.2) improved "visual voicemail with Bluetooth support, a refreshed mobile hotspot app, and a fix to prevent data connections from dropping as you move between WiFi and 3G coverage." Android Central also points out that Adobe Flash 10.1 came bundled with the update and should work immediately.
However, it is still a good idea to head over to the Android Market and make sure you are running the latest version of Flash Player after the security flaw last week.
For those of you who don't know how to check for updates and haven't gotten the notification yet, head into Settings / About / System Updates to check if the update is availabile for download.
Maybe now we'll have a few less threads in the forums that won't be questions about when Android 2.2 is coming for the Droid X. Our very own Jay Kramer informed me that the update was coming, and he is already installing it.
Image from Android Central