The best replacement for msp430 is pic.

The best alternatives to msp430 are rated as following:
★★★★★  pic
★★★★★  avr
★★★★★  arduino
★★★  pic24
★★  stm32
★★  cortex m3
★★  8051
★★  arm cortex m3
★★  stellaris
★  cortex m0
★  c2000
★  efm32
★  atmega
  attiny

Your alternative for msp430 is not listed? Suggest!
Speaking about msp430, one probably shouldn't forget about zigbee.

Other search terms related to msp430 and their ratings are:
★★★★★ zigbee
★★ xbee
★ pwm
You have in mind a companion for msp430 and it is not yet here? Propose!



Google Trends

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msp430
pic
avr