I recently bought two Atmel SAM chips, but I'm also planning to use STM chips, since I'm interested in the OpenPilot multicopter board. Probably I also will use LPC chips, since they are used in the microcontroller class at my university.
In opposite to 8 bit MCUs of different manufacturers, ARM Chips build upon a standard. Does that mean, that everything or most of what you explain on the STM chip, also applys to the SAM chips?