I just bought two new Arduino R3 boards. The serial to USB still doesn't work at 300 baud.
This bug was identified in 2011 http://code.google.com/p/arduino/issues/detail?id=542
Reported by dmel...@gmail.com, May 14, 2011
The ATmega8U2 firmware overflows UBBR at 300 baud because it sets the U2X bit, yielding a setting that overflows the 12-bits. This was masked previously because the Arduino core contained the same bug: ( issue #522 ). I'm fixing that bug, though, so we should fix the firmware too.
I looked at the firmware and the fix is easy. Why do we still have this bug in 2014?
Guess posting this makes me feel a bit better, sigh.