Mostly a hoarder. I have only used mileage twice.
I have about 275K lifetime on NW, used for 2 flights.
March 02: Used BUF-STL so I could go to a conference there, lowest fares were upper $300's, which seemed ridiculous off season, over that short of a distance. Glad I went cause got to know my now wife at that conference.
June 04: We spent 200K of NW mileage on BUF-FCO for our honeymoon! So mostly hoarder, but spender when well worth it!!!
I have around 40K on Delta, I think 28K on US Airways, a few segments here and there on AirTran, JetBlue, and Southwest that I don't have a good handle on.
I was getting close on Vanguard Airlines before they went broke. A couple of flights BUF-MDW and BUF-MCI. They were great for keeping Midwest flights low here, I miss them.