Since I'm not using Polychain mode with multiple OB6 Modules, I'm sticking with firmware 1.2.0 which came with my unit and has been working perfectly fine for over a year now.
I had tried later revisions, and the LED brightness inconsistency has annoyed me more than anything else. I've been told by Sequential Support that since my unit is an early hardware version, the LED problem cannot be fixed in later firmware (although with the 1.2.0 firmware the LEDs all show exactly the same brightness all around, so that's why I'll stick with that one).