As far as I am aware DAL's policy has not changed. Just show up at the ticket counter and list for it. Sometimes you have to pay departure taxes and sometimes you dont. Seat in the back only I am sure unless you are online. Thinking about doing that myself in july. Just make sure you are on the list first.
Same for USAir. Did it last month. Taxes are 'round $14 to Paris, but did not pay to come back to the US. Must fly in the back. Make sure to bring an extra jumpseat form with you (the gate agents in Paris claimed they had none left). Note that I'm a USAir Xpress guy, but should be the same process for anybody else
Anyone jumped the pond with Delta lately? How was t?