I followed the Kickstarter campaign for a while but then I almost forgot about the Spark Core, which have finally become available. At first glance, the HW design looks solid and it comes with a complete open-source stack, including the hardware design, the firmware for the STM32 and infrastructure/server components.
Other hackers have already become creative, which, to me, indicates a high level of versatility/hackability. It also promises a swifter speed of development compared to other solutions for similar use cases, where you want something ATMega/Arduino-ish in a small package but with full network accessibility:
The light control system I had always in my mind seems rather close now, with a couple of these and some glue parts + infrastructure, so we'll have to get a couple of them to build and publish it :)