I have updated both EX58 rigs from F4J to F4M bios and can constitute the following:

- OC from F4J still stable
- added command rate option (0-3 lol.. only used 1 and 2 so far). 2 for all slots populated, 1 for 3 slots populated works fine for me
- RAID manager init maybe 2s faster, also it seems to do less "reboot loops" when changing settings
- slightly higher bandwidth when compared to F4J at identical settings
- F4M supposedly fixes some visualisation bug so taht's always a good thing
- Ram settings can now be keyed-in directly, helps but still annoying to set stuff for each channel individually
- voltages now turn pink if you get near "dangerous" voltages


That's about it, all in all I can recommend F4M over F4J as the best current bios for the Extreme. Haven't tried final F4 and F5a, as most people here seem to agree they suck.