My friend mines ETC on nanopool, 0% rejection
Second this, been mining ETC on nanopool since the addition. Been stable so far with low to 0% rejection.
I am in Europe and use the EU pool. The ping time is about 40ms. But the rejection rate is more than 20%.
I am not too sure thou. I am mining at their Asia pool. Also they seem to have some issues with EU1 server (source: their twitter update).