I have a few reservations though...
The hardboard seems to do a good job of highlighting hollows in the floor, so while it might be a flatter surface overall, it also bounces a bit where the underlying floor is uneven.
The back-to-wall units go all the way to the floor, they're not the sort on legs with clip-on fascias, so he's talking about sitting them on top of the vinyl - which happens to be the plushest / deepest we could find (and the hardboard below that) which might make the vinyl "lift" slightly around load-bearing edges for the units etc.
If the vinyl needs replacing, this then causes problems with essentially needing to gut the room to get the new stuff in - unless i'm missing something obvious :-}
The only way around it that I can see would be to run a blade around the fixtures and fit the new vinyl up to the edges, but that'd look a bit crap, even with silicone to seal the edges.
Any ideas on best practice in these circumstances would be welcome :-}