Switched from printf_P to Serial.print to prevent all kinds of nasty PROGMEM troubles. Distinguish between 32- and 16-bit architectures when reading ptrs from flash. Ditched #defines MINIMAL & SERIAL_DEBUG. Debugging code is now only included when DEBUG is defined. If your target (e.g. ATTiny) cannot handle the extra code, then don't enable DEBUG. #defining DEBUG will now also output a register-dump on calling begin() of NRF24 driver to aid in (connection) problems.
For information on installing libraries, see: http://arduino.cc/en/Guide/Libraries