The nights and flights is an SPG redemption option were you redeem five free nights and 50,000 air miles together. This promotion saves you up to 20,000 SPG points so that you get the extra 50,000 miles for just 20-30k points instead of the normal 40k it costs. You have to stay at a Category 3-4 hotel and can only transfer to airlines with a 1:1 Starpoints-to-miles exchange rate.
In our example, we booked 5 nights at the Sheraton Park Hotel at the Anaheim Resort for our DL trip. Booking 5 nights gets you the 5th night free. At first, that was all I did for 40k points. But then I decided that since I had the balance available, it made sense to take advantage of the Nights and Fights offer. You have to call in to redeem it, but it was very easy. So for 30k more points (total of 70k), I got 50k Delta miles on top of the free hotel nights. The cost for the miles in term of average SPG points value was $660. The cost for the hotel was $880. But at the time, the room would have cost us closer to $1100 if paid out of pocket. So basically, I felt like I was getting 50k miles for $440 in value, or 0.0088 cents per mile, which is decent value.
We didn't need the miles for that trip. I used 25k of them to fly DH down to Austin during my work trip in January so that he could hang out with my brother and sister in law. That flight would have cost $450 out of pocket. The other 25k are still hanging out in my account waiting for a use.