I have MK808 and MK802IV so I'm kinda interested in your ubuntu-mini
My main goal is to run motion on those devices. So far my long-term tests on Rockchip devices constantly fail. Most issues are USB related: /dev/video0 disappears or fail to respond. Sometimes devie may die with out of memory killing essential processes like wpa_supplicant or irqbalancer.
I have also MK802II which is based on Alwinner A10 and it was running motion for almost 1 year (!!!) without interrupt. I only turned it off once to change power adapter. So I believe motion has great potential running on low power ARM.
If you need to perform some more testing - ping me I would be happy to assist