I'm going to rank here the best airline to nonrev on in my experience.
1. Continental
2. Alaska
3. JetBlue
4. United
5. US Airways
6. American
7. Northwest
I won't count AirTrash(Overqualified) or Delta(Never Nonrevved)
I'll date myself by saying that Delta used to be preferred. They would complementary upgrade even if you were traveling with small children. AA was ok, not anything great and Eastern was the backup when you couldn't get on DL. Then again most of my OA travel was done a while back.