I have been using stm32 controllers (arm based) and all the positive energy from the arduino micro's have got my attention. I purchased a uno because i am building a cnc and know that grbl can run on an arduino with no problems. As far as i know there isnt a gcode interpreter that can be ported to the stm32 with out a lot of work.
My question is really about the arduino software and if the arduino software makes use of all the features of the 32 bit processors so that you do not get limited by the software environment which is kind of targeted to non-engineers.
Underneath the "non-engineer" layer, you have a real C/C++ compiler, so you're free to do pretty much anything you want.
But the various pre-written Arduino libraries are unlikely to support the more advanced capabilities of 32bit chip peripherals.
See http://stm32duino.com/ for Arduino IDE support of (some) STM32 chips.
I keep meaning to check out stm32duino. The STM32 chips have capabilities beyond the wildest dreams of the AVR line.
As long as standard C is available to me then it's like having the best of both worlds.
Having the arduino libraries for ethernet, wireless etc...is great since I don't know if I could successfully code that stuff on my own.
DrAzzy: the stm32 chips have so much functionality it will make your head spin. The biggest shock from going from an 8 bit to a 32 bit arm is the number of registers. The registers are all organized well though, so it's not so bad.