Delta non-rev benefits are great. They are probably the best in the industry. That being said, first class upgrades are offered to pretty much everyone. Medallions of any color (silver, gold, platinum, diamond) are offered for free, then everyone else can pay a fee at the gate if there are any seats left (there never are). The flights to anywhere worth going to are always full. I consider a flight open if it leaves with more than 10 open seats. Unfortunately, you never know it will leave with that many until departure time. I like our benefits, but they are not worth much due to our extremely high load factors.