1) GPS Glitch protection - gps positions are compared with the previous gps position. Position accepted if within 10m or copter could have reached the position with max accel of 10m/s/s.
2) Bug fix for pixhawk SPI bus contention that could lead to corrupted accelerometer values on pixhawk resolved
3) Auto Tuning (compile time option only add "#define AUTOTUNE ENABLED" to APM_Config.h and set CH7_Opt or CH8_Opt parameter to 17)
4) CPU Performance improvement when reading from MPU6k for APM
5) SUPER_SIMPLE parameter changed to a bit map to allow some flight modes to use super simpler while others use regular simple (MP release to allow easier selection will go out with AC3.1 official release)
6) Safety changes:
a) safety button must be pushed before arming on pixhawk
b) RGB LED (aka toshiba led) changed so that disarmed flashes, armed is either blue (if no gps lock) or green (if gps lock)