Dave - I'm glad to hear the sound of the built-in mics has been improved. The ones in the 600 were ok to start with, but the marked difference of even an inexpensive dynamic mic was really noticeable.
Like you, I don't like my recorded voice, but found it did sound better switching to a condensor from the Shures. I tried micing the acoustic wiht a 57 and 58 one time, one pointed towards the 12th fret, the other to the bridge/soundhole spot, but didn't find it any improvement over a general 15th fret pointed 57 by itself.