OK figured some things out, some good:
1. It's quite easy to revert to fastpath, so it's no longer a 1 way trip. I'll add this to the guide with the proper memory read checks, but just so you know it's possible (I don't recommend actually following this yet, a lot of things need to be verified):
Quanta Revert - Pastebin.com
(EDIT: don't follow this. it's missing a lot of important uboot environment variables. wait until it's in the guide)
2. The unique base MAC of your switch (that each port/vlan gets iterated on) is stored in EEPROM. When flashing to brocade, it now has no idea how to read that EEPROM (Brocade expects it to be in a different part of EEPROM), so it defaults to 00e0.5200.0100. On it's own this isn't a problem, but if you have multiple flashed LB6M's on the same l2 network, you're obviously going to have some collision issues. There's an easy command to change the base MAC to resolve this, I will also be adding this to the guide (along with how to fix the weird serial number, and set it to what you want) - This makes it a good idea to note down the base MAC of your quanta before flashing. I don't think there's a sticker with this anywhere on them usually, so after flashing it's gone and you'll need to set it to a randomly generated MAC (nothing wrong with this, though)
3. Under Brocade, you can slow the fans down. at configure terminal level, do "fan-speed 1" and it'll slow them down to level 1 permanently instead of auto-cycling through the 3 fan speed levels. Just keep an eye on your temps, mine went from 30c to 45c which is still fine, but could be worse for people in different environments. There's also "set-pwr-fan-speed" which controls the speed of the fans in the power supplies, but I haven't messed with it yet
If any of you still have a stock unflashed LB6M, I *REALLY* need the output of the command "printenv" in the quanta bootloader