GNG is offering a $0.10/therm discount for their 12-month fixed plan, but it's mutually exclusive to the Delta bonus offer (you can't qualify for both). So if you burn through more than 1000-1500 therms per year, it makes more sense to take the cash discount rather than the Delta miles.

You can still sign up for the 1 mile/dollar part of the offer regardless.

If anyone has managed to qualify for both discounts, I would be interested in hearing from you.