That WiFiSpi system looks nice.
I really like that the firmware is an Arduino sketch. I think that will make it much easier for people to install the firmware using the Arduino IDE compared to the headaches of trying to flash the AT firmware. And of course this makes it so easy to read the firmware source code and make modifications.
The availability of a shield with the firmware already installed would make it even easier. Using AT commands is attractive when the ESP8266 ships with the AT firmware already installed.
I wonder how AT vs SPI compares in terms of overhead and performance?