Power_Broker:
I use the Teensy 3.5 for several undergraduate research projects as well as for my RC plane. I can honestly say that that MCU is the best one out there in terms of hobby grade stuff. It has amazing processing power, has a fast clock, several serial/I2C/SPI ports, 16bit ADC, 5V tolerant, and is affordable. It's also really easy to use since you can code it using the Arduino IDE.
Yes, I got a Teensy 3.5 fairly recently and so far I have been greatly enjoying the speed of floating point calculations!