What kind of hashrates are possible with this firmware?
Also should I update to the latest dev release or stick to latest stable (?) build?
you can crank the freq and power up , stick with stable release
just boot it, flash nand option , reboot and edit services > cgminer = add pools and there you can adjust volts and freq, or use scale option and start at like 1.10 and go to 1.15 and 1.20 and so on
and set the desired c temp , its the best firmware as it loads faster and gives real time gui so you can see if the hw errors start stacking up then adjust cgminer settings
NOTE : if you have freq and power settings and then change the scaling option the scale will apply to the chain settings