I have been working with the AWS IoT starter kit from Marvell Semiconductors for the last 2 months and I have to say I am pretty impressed.
It's nothing like the microcontroller boards that I have worked with before : Arduino, ESP8266, Particle Photon and core. It doesn't support Python or a processing like syntax. It supports good ol C. It's not even 100% open source. It doesn't even have a lot of community support (yet).
Ok, so now we know what the board it not. Let's see what the board is.
Based on a wireless MCU which is being used in consumer appliances and products. This is where I think almost all of the maker-grade development boards fall short.
Plus it is based on FreeRTOS, which has it's own support ecosystem with plenty of libraries.
Open source SDK for Amazon's AWS IoT
Releases happen quite frequently, and there is active discussion on the chat channel as well as issues page.
It supports gcc-arm and OpenOCD, and also works well with Eclipse CDT.
As a Cortex M4F with 512k SRAM clocked at 200Mhz, it packs quite a punch. Plus it has something known as XIP which executes code directly from your flash, without loading it in your ram first. This makes it easier to have a flash chip of your exact requirements without paying up for a large ram.
Plenty of peripherals including USB (video as well as audio), DAC, I2S as well as SPI, I2C, UART, PWM and ADC. So all your existing sensor breakouts will work.