Suppose I stay 2 consecutive nights at the same hotel, pay for one night, and use points or a certificate for the other night. Will I get credit for a stay towards my Mega Bonus?
In the Terms and Conditions it says: "Nights spent while redeeming an award are not eligible for credit."
absolutely you will. You get credit for 1 nights stay.
Shoeman is correct. You will get credit for the one paid night.