Unless careful it is very easy to get burned with Amex POT. By all means take it for the promo awards points, but wouldn't use it or do so carefully.
There are two versions if am correct; one is automatic, other is Pay Over Time Select.
With the latter it's basically like a line of credit from AMEX. With the new website POT is displayed (for those enrolled), and if you want to use it click on like to "see what charges are available" to be moved over to POT. Only certain travel, entertainment and few other things qualify, so if nothing like that is on your current bill, then that is that. If there is system will show which charges are eligible, you check ones want to move, click, and things are moved over (subject to approval).
Other version is far more dangerous, and have seen many fingers burned.
This is the automatic "Pay Over Time" where any qualifying charge made on your AMEX is moved over soon as it posts, not at say end of your billing cycle. Worse you'll begin accruing interest from day one charges are moved over to POT (no grace period). Also once you've moved something over to POT that's it, cannot get it back out.
There's even more fun; like a cash advance you cannot get at the POT balance without paying off any regular charges first. So if you have a POT balance of $3000, an Amex payment due on 12th for $5000, and current charges (for next billing cycle) of $2000 you'd have to pay the $7000 first, then any excess would go to the POT balance. This or you can simply pay entire balance (total due for statement, new charges, and POT) all at once. In short payments in excess of current balance due will be applied to next month's bill first (if any), then POT balance.
Clearly as with those debt consolidation loans Amex has been offering they are getting into the banking business seeking to make money off interest. That is the only reason why POT exists IMHO.
While there may not be a "gimmick" I'd make very sure when enrolling in POT that it isn't the automatic version. Pay Over Time "Select" is indeed harmless. Long as you don't transfer anything into it, and or are aware of what is going on , should be fine. But quite honestly anyone with a halfway decent credit score should have a CC with lower APR than Amex is offering.