Going on the MX6 specs[1] and GFLOPS alone[2], it should be a bit faster than Ouya's Tegra for the cheapest option and handily beat it on the more expensive models. Bitcoin mining is out of the question - it's basically a tablet-class GPU.

GFLOPS isn't the whole picture of course, but my Google-fu is failing me at the moment.

[1]: http://en.wikipedia.org/wiki/I.MX#i.MX6x_series [2]: http://www.cnx-software.com/2013/01/19/gpus-comparison-arm-m...