Paul Stoffregen and PJRC has run a kickstarter campaign to fund the development of an Arduino-compatible device based on an Arm Cortex M4: The Teensy 3.0.
The idea is to take the easy of programming an Arduino and the power of an M4. Given the component prices, the cost to the end user will be about the same. The only difference is that the Arm runs at 48MHz, sports more RAM, more FLASH and a whole bunch of useful I/Os. For instance, I2C, I2S, SPI, UARTs, PWMs, timers, ADs, etc. You also get DSP capabilities, as well as multiple DMA channels. All in all, more power!
And the kickstarter? They asked for $5000 and got $70.874!