Si:
I just don't get the Due concept. I just feel I must be missing something obvious. Someone please explain it to me.
Surely, if I need more processor, then its because I'm doing something fundamentally unsuited to an operating system-less device like the Arduino. I.e., image processing, DSP, MP3 playing etc. If I need an OS I'd have Linux on a Raspberry Pi.
Arduino is a device for electronic hobbyists. 16 million things a second is faster than I've ever needed an Arduino to perform.
Surprised so much of this discussion has centered around the processor as apposed to I/O.
Due 96 MHz, 54 digital I/O, 16 Analog Inputs (assuming it's I/O is the same as Mega)
RPI 700 MHz, 17 digital I/O, 0 Analog Inputs
If your project involves a lot of low level I/O with any appreciable sensor timing and filtering, Due sure seems to make much more sense to me. The quad/multi copter crowd and home energy monitor crowd are eager for the power. Large amounts of I/O require rather expensive hardware to interfce to the RPI via USB or a multiplexor on I2C which is relatively slow.
I have a home energy monitor on a Mega that uses 44 digital lines and 8 analog. Monitoring HVAC status/run time, water pressure, water pump usage, water heater run times. Have an ultrasonic sensor on the oil tank measuring fluid level. Have sensors on the power lines coming in to the house calculating energy usage "real time". All this is logging to a MySQL data base on the NAS. Also monitoring eight wifi enabled thermostats. I sends out a plethera of alerts via LAN when certain adverse conditions are met. There are (4) Windows 7 machines in the house each banging away on the LAN wih their polluting flood of device discovery messages (arduino has to process all of these that are pointed at it) , and the ATT Uverse router banging away with DHCP status messaging. The Mega can get pretty taxed. I have isues with the fluid level sensor and power monitoring when all of these things manage to stack up on top of each other. Could I do all this with a PC...yes, but every time I've looked into it, the cost gets excessive quickly. My $50 Mega, $20 ethernet shield, and $20 in various opto isolators and resistors is much cheaper, plus it doesn't consume nearly the power the PC based system would.
From my perspective, RPI is a small personal computer, not a microprocessor for imbedded logic projects. I don't need the USB ports, video support, or other peripherals on the RPI. I'm near the front of the line for a Due.