I was using it the context of controlling the "eye" of a wheeled robot so both the eye and the robot could follow faces. 2FPS was workable on this but 320x300 didn't give it much of a field of view.
From $35 4x1.5Ghz Cortex-A5 ODROID-C1 to $99 octa-core Exynos5422 ODROID-XU3 Lite (4x1.8Ghz Cortex-A15, 4x1.3GHz Coretex-A7, plus OpenCL 1.1)
They have their own ecosystem and monthly magazine (sic!). Raspberry Pi is one of the first and most popular; it's great for beginners, but if you really need to push the envelope there is always competition that tries to undercut them in price, performance and/or features. Now again, RPi 2 has set a new bar, but it is not that high.
While certainly most popular, I'd dispute the claim of being first. For example BeagleBoard was initially released in 2008.
So the C1 and related boards look great but I'm cautious of building around something with a smaller community just because of the potential for it taking far longer to troubleshoot the underlying stuff I need setup to work on the actual project. That said I'm pretty sure I'll succumb to a c1 in the next couple of months!