Production FCDs thus far have all been shipped with firmware release 18b. This has been through months of proving both before and after production release.
This firmware has been in existence since October 2010, and there have been four firmware releases since then, all of which are designed to be backwards compatible.
This means that should you decide to install the latest, 18f, firmware, it should not break anything you were doing already on an earlier version of firmware, and if it does, let me know!
The newer firmware updates have been made available to provide a much more comprehensive API for third party deveopers, so you will quite likely find that there will be prerequisites from host software for certain firmware versions.
Installing new firmware should only take a minute or so, and as well as updated firmware there’s also a guide in the downlaod section.