Correct me if I'm wrong, but isn't this true for all popular ARM boards today? Decent CPU, low power consumption, and terrible I/O performance?

I remember the PandaBoard as exceptionally bad, most are better but still pretty slow.

Take a look at the BeagleBone Black. It has pretty decent I/O. The big gaping missing piece, of course, is better video output, but that's sort of in the same bucket as open source GPUs: missing in action.

I actually have one on my desk, waiting to be used. Hoping to play around with OpenBSD on it.