I've used miles for a domestic first award once (well, technically business...). In that case, there were blackout dates on the saver awards for the dates I needed to fly. And most of the days around the blackout days, were sold out. For 40,000 miles I could have booked a standard award in coach without blackout restrictions. Or for the same 40,000, I could book a 1st class award. Needless to say, I booked the FC award, and ended up traveling in business in the upper deck of a 747!

I've never booked an international award. Most of my pond-crossing has been in the off season, where it's easy to get 3-5 seats to yourself. Pop up the armrests and you have a nice 'economy class' bed. (Albeit minus the 'socks')