Greetings,
I have the HD3P running F5. As you can see, none of my systems are running the absolute latest BIOS that might be available.
Notable enhancements (F14):
IRST updated
Future BIOS' will support NTFS: Add NTFS format support for Q-Flash
Addresses memory compatibility
Security fixes
I am not saying that CPU microcode vulnerabilities are insignificant or should be ignored, but in many cases, the exploits require a level of system access that someone "outside" wouldn't generally possess, making the probability of being compromised extremely low. This and what dmdilks mentioned regarding not being able to go back would make me reluctant to upgrade unless I was trying to address a specific issue or add support for something necessary. If you upgrade to F14 and something doesn't work (the way you want), you would be stuck there. F14 is also the first release after several beta iterations.
If you are experiencing an issue (one that is addressed) in F14, then upgrade. If not, there is no need to do so.