Whatever else you can say, you can't say that the 'whole country' is behind the McCanns.
A lot of people who I talked to about it over the years have agreed with me that A) they should not have left the children unattended - not even using the hotels child-minding service - and B) that their behaviour afterwards was a bit strange as Eli says. while it is a tragedy for them they are at least in part to blame for it themselves, and certainly do not deserve to get so much more media attention etc than any of the other families whose kids go missing. The whole thing is media-hyped, partly as a result of a very successful campaign on the part of the parents - and I guess one has to admire their ability in this area if nothing else!
Yes, the cops will (hopefully) learn some from the exercise, but they probably need to learn quite a lot before they can gain from the co-operation - for example who many Portuguese-speakers are there in the Met? And it is one heck of a 'cold' case...