Good fortune, I'm in at $6 with all my money out (multiple times over) and just letting the profit ride. You should be fine, market cap will work toward MRK's 1.37 billion and then some. Enjoy the ride.
Also, if you do a little homework, you can see that a number of insiders are choosing to exercise and hold, which tells you how strongly they believe in the stock. General advise is to ALWAYS exercise and SELL, because of the sever risk associated with tax consequences. If you exercise at a high price, you have to pay the tax at that price, even if your stock drops to nothing. Not a good situation and the reason you generally see same day sales.