I got it too and as noted here, they cleverly (?) left a period in December and early January where there was no program in force so I got no credit for a stay then. Not that I have been able to use the credit ever anyhow! If you book through a FSPP, you already get the upgrade if available (apparently it's not confirmable either way) and they don't allow you to "stack" them.

There is no customised experience or exclusive access that I've ever seen, this is simply puffery. The only additional benefit for someone who uses FSPP is free internet in those hotels that still charge for it. This is one meaningless program unless maybe if you are on a corporate rate.