Why use a 14.7456 Crystal instead of 16 MHz?

Because the 14.7456 allows the use of much higher standard baud rates, up to 230 KBaud.  The highest standard baud rate attainable with a 16 MHz crystal is 38 KBaud.  The 16 MHz crystal is capable of baud rates up to 1 MBaud if it can find something to talk back at its non-standard baud rates (another AVR would do).  Of course high baud rates may not be that important to you.  Swap out to a 16 MHz crystal.  The board has a socket allowing easy crystal changes.  The MAX221 I use on the board to convert to RS-232 is good for 250 KBaud.

While on the crystal frequency topic, Atmel notes that power demand rises substantially at values above 8 MHz as a full 5 volt swing is required.  They have not yet published the numbers but I'm guessing that the power triples when going from 8 MHz to 16MHz.

Also, for you on-the-edge power freaks, I have tried running the 128 with a 22.1 MHz crystal and it worked just fine.  No extensive testing, but it would talk at 115KBaud no problem.

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