Most people discussed the use of 5/8" OSB or ply over the Platon/Delta. Platon literature however, indicates that if you use laminate flooring you do not need a subfloor AT ALL. You can lay it directly over the Platon (with the thin foam sheeting underneath, of course). Here's where I'm looking for opinions. After putting down the Platon over 3/4 of my basement (+/- 1000 sq ft) I find it has ripples in certain areas that don't settle fully. If I try to smooth them they just pop up nearby. They aren't major but enough to cause worry. I suspect it is due to the fact that over the full expanse, the basement (4 yr old)concrete floor is not perfectly level.

Do you think the weight of laminate flooring is enough to weight down the Platon? Would I be asking for trouble? It seems to me that subfloor or not (if the surface is not perfectly level)laminate over a large expanse might end up "hanging" here and there. Any pointers?

A properly poured basement floor is not supposed to be level. It should slope toward one or more floor drains. So you have some shimming to do. When I've had laminate installed abovegrade in old homes, the installers have made imaginative use of cedar shakes.

At first I had planned to build the room walls right on top of the Platon to keep a continuous vapor barrier from wall to wall. I was told by Platon people that it can be done. But, I think it will be easier and with fewer unknowns to put down the bottom wall plates directy on the slab and deal with the Platon and laminate on a smaller room by room basis. Should there ever be a water event it would be easier to pull up materials locally. Avoiding subfloor this way keeps cost down but it also is one less thing to tear up and discard should there be a water problem.

I don't work fast but I will report on results and any course changes that I might make.

Strips of 1/2" extruded polystyrene under the plates will protect the wall from water vapour moving up into the wall and from any minor flooding.