Funny this was brought up as I just returned from a reward ticket on AS (using CO miles). I am MVP/Gold and was travelling with 3 other adults, all on the same itinerary, all award tickets. We had 4 segments, DEN-SEA-ANC-SEA-DEN and I asked at each station about upgrading our seats. I was always offered the purchase deal but declined since we didn't think it was worth it, however on the last leg, SEA was virtually empty (Sunday before Labor Day) and it turned out no one was in 1st Class at all....picked an "approachable" agent who upgraded all 4 of us, no questions asked (after I showed my Gold card of course). I was a bit surprised as he even had to call control to clear moving us (so few pax that the flight was sort of weight restricted in that no one could move out of their assigned seats until after takeoff). So it's always worth asking!

-Mike