I have a miner coming in batch 1a (the "second batch", which was miners that were reserved, but not paid, shipping September 18-25), and I'm kind of concerned about time for ROI. If the price stays the same, things will be ok, but given the number of miners flooding the market, and the volatility that coins have seen recently, I'm concerned. I know I'll reach ROI, but instead of being weeks, I think it will definitely be a month or more, and by next year, if the number of miners have been sold that people are speculating have been sold, it's possible that owning a single D3 will no longer be profitable on its own.
I may be being pessimistic, but being a pessimist hasn't ever made me completely disappointed in the outcome.