As a high cost producer this is how I see things going down with ML:
If copper/moly prices tank and continue to stay low, then ML becomes the next BAJ or CMK at the best case scenario, or GBG at worst as they can't sustain continued losses and low prices without significant cuts to their costs.
If copper/moly prices tank and then rise back up, ML tanks because then everyone thinks its going under but in reality it becomes a great buy as soon as those prices recover.
If copper/moly prices move up from here, ML has one of the best upsides out of all similar mining stocks because as a high cost producer, it is most leveraged to the prices of the metals it digs out of the ground - to the negative and positive.
So your decision to invest or sell ML is strongly related to where you think copper/moly prices will be, even moreso than any similar stock because ML might not survive the next sustained copper/moly bear market but if no such thing happens, it has a very great upside.
FWIW, I'm in wait and see mode. The market is looking toppy in general and although ML and copper haven't really participated in those gains, they are at risk of particpating in any possible losses in capital market prices across the board. I'm of the opinion that moly and copper will be in a short-term bear market which means they and ML will bottom out during the summer then come back strong 2nd half of 2013.