My grandmother and her sister were recently bumped on a DTW-FLL ns and received a $300 credit voucher. NW wanted to put them on a connecting flight and I think bump them up a class, but they opted to go NS on a later flight instead to Miami.

I think they also received a meal voucher, but didn't mention an Amenity pack or discount off future travel.

In their case, though they didn't realize it at the time a r/t voucher may have been better. They knew of future travel plans to ATL and when they wen to book it was $324 so they had to fork out money towards the fare... On the same token, who knows if award seating would have been available on their "ideal" itinerary.