The entire idea behind my post was essentially that the Delta card is one of the easier amex credit cards to get approved for, as opposed to say blue/clear/etc. While there are some people for whom those cards could be worthwhile, by all means convert to one of the other products as you get the card and before the year without the fee expires.
While there are some exceptions, generally any charge card can be converted into another charge. Similar for credit. The one card, while may be appropriate for some, was thought up as a mix of credit/charge, and in a way is neither. Thus, you won't be able to convert it to anything. If it works for you, great. Although if you're just looking to get a foot in the door but don't like the card (as you can get better than the 1%, and the apr they pay on the savings account), it may not be the best choice.