I'm having the same experience right now. I had to fly to an airport hotel at DFW for a one-day meeting. I got 36 hours notice.

So I'm in the far, far, far back of a state-of-the art MD-80 both ways. At least I scored an aisle on row 26 on the return. I got a middle on the outbound tonight.

The outbound was completely full.

I've also had to do a couple DL flights lately, and had much better luck getting decent seats.