tremw:
If you register with FRO and are the support recipient, FRO will enforce the support order by collecting the payments from your spouse's employer (or other income sources) and depositing the funds into your bank account. That way, if you're not sure you will receive support payments directly from your spouse on a regular basis, you won't have to worry.
Many people here have posted horror stories about their dealings with FRO, but my experience has been mostly positive. I ran into a couple of problems, so I wrote to them outlining the details, and the problems were rectified.
If you're the support payor, you may choose to pay support directly to your spouse and avoid FRO altogether. I've read that in some cases, if a court order is changed, it takes FRO a while to update the payments.
If you do decide to register with FRO, you can opt out at any time; however, if you want to opt back in again, I think there might be a charge.
Linda
