It's understated on the kickstarter, but it looks like this is a vehicle for a new cloud development environment:
You can program your new software in our web development environment or in your favorite text editor, and with a single click, Spark Flash delivers updated firmware to your project over the web.
This could (or would have in my case) been very handy for prototyping wearables. BT4.0 is better for battery usage and phone connectivity in production-ready wearables though.
This is much smaller than most Arduinos (certainly smaller than the official Arduinos).
Processor-wise I guess it should be comparable to the Arduino Due (http://arduino.cc/en/Main/ArduinoBoardDue) which has an 84 MHz Cortex-M3 (the Spark Core runs at 72 MHz). The Core seems to have more code space, with a 2 MB external flash.
There's an incredible amount of value in "well-integrated". I wasted weeks trying to get an Arduino to have enough control over an Xbee to get it to even see wifi networks. And Xbees were designed to work over existing wifi frequencies...
That's brilliant. Is there any way to get a wifi module like this on the Raspberry Pi? All the ones I've found require external power (i.e. a USB hub)...
I've used both of these without a hub without any problem. I use an old Samsung cell charger (I think 700ma). I don't generally have anything else drawing power from the USB port though.
Edit: they made it way cooler than I ever dreamed of making mine.