I have UAL, AA and Delta miles (lots thanks to FT).

IMHO, the Delta miles are pretty much worthless 'cause you just can't get seats. I tried recently to go to OZ in biz or F, Delta had zip (at any rational use of miles), UAL and AA at least had something.

Delta did have availability in coach--but, for the miles they wanted I'd rather buy a coach ticket and rack up some miles on AA or UAL.

However, I did recently use 3200 Delta miles for a sub to The Economist. Value around $90-100.