I looked into these devices a bit more last night. It seems Picuntu (which is based upon Ubuntu 12.10 and still in beta) currently only supports the dual-core RK3066 devices and I failed to find any success stories of people having got Ubuntu (or any non-Android Linux) to install on the quad core RK3188s.
Picuntu doesn't yet include the Mali GPU drivers but there are instructions available for installing the Mali drivers which apparently brings you accelerated 2D and OGLES2 under xorg. However, its the VPU which handles video playback accel and I'm not sure this is working yet for the RK3066.
Another pitfall is the wifi/bt chipsets as, having a read through forums for these devices, it would seem not all the wifi chipsets are supported by Picuntu yet so thats another thing to look out for before anyone takes the plunge and buys one.