Since they're allowing you to choose the date of your payment you may get your statue later than people who pay when the statue releases. Unless of course you call them when a statue is being released and tell them to force the payment. Then you'll get yours processed the same as the others.
You will not get your NRD back and they will take a fee for processing back the payments, but yes you get the rest of the money back.
Exactly, it's a great option.
I've only done this about 6 times, and it does make thing easier over all.
Sometimes you get them earlier than people that pay in full. If they get an order in a few days before a flex payment date they will try to get all the flex orders out 1st instead of pushing them to the next month. I have had that happen a few times.
I have canceled 4 figures and two statues in the past several months and got my NRD back or moved every time. If a figure is really delayed (and they always are) they will give you your NRD back. If they don't give it back there is a good chance they will move it to another figure. This will not happen all the time but I have been lucky i guess.
I flex a few things and most I pay when it comes in. It's a nice option for crazy expensive things like the batmobile.