For those using the I94 form for land crossings into the US, you'll be able to pay online and do that up to 7 days prior to the land trip into the US.

Not sure how much this slows down things at road crossings overall, but this kind of stuff being allowed at least prior to showing up at the crossing should help some.

If you don't use it with the week, however, it wouldn't surprise me if CBP refuses to refund the money in full..