The only difference between OS 2.3 and 2.2 is that 2.3 uses ATmega1284p and 2.2 uses ATmega644p. Because this upgrade went ahead of plan, we haven’t properly documented the difference yet. At the moment the firmware is the same for both, although 2.3 is clearly has more flash memory space and RAM space for future upgrades. As I said, the main reason we upgraded is that ATmega1284p ends up costing less than ATmega644p.