Lefty, could you shed some light on this issue? Thanks.
Honestly I've never even tried to test all baud rate in the past on any of my arduino and variants, under the assumption that if it works at 115200, it should at all lower rates.
It's been some time and many IDE versions ago, so I can't recall the details, but I'm sure I was seeing baudrate garble problems with just the IDE's serial monitor on some baudrates when I ran some simple tests. May or may not still be the case but seeing your test results reminded me of those past things I saw.
Anyway just ran tests at all Arduino IDE serial monitor baudrate options offered (why is there no 600 baud option?), and all speeds ran fine, except for 300 baud which garbles. I seem to recall that is because of some baudrate divider option (doublespeed?) bit is set up in the AVR by either the bootloader or the serial library.
Anyway this latest test was performed on a Seeeduino FTDI equiped mega board, IDE 22, Windows XP pro SP3.