Now using get_username and associated functions with the new_user and unlock functions.  Re-wrote main loop and so it's simpler and uses more functions, it's easier to follow that way.  All previous functionality (nvm writing/reading, patter drawing/sensing still appears to be working.  By the way, SPI clock is still 667kHz, now using two parallel 100pF caps on the SCK line, going from SCK on the PIC24 to ground.  Seems to work a lot better than before.