I am learning Dutch and I love to fly to the Netherlands to practice. But there are strange things going on there. First, the authorities mandated Mode-S transponders for all GA aircraft. Now as a direct consequence, “the radar clutter is increased to such an extent that Schiphol Approach cannot properly provide air traffic control.”
The result: they have banned VFR traffic in a vast area of the country around Amsterdam between the coast and the Ijsselmeer. Flights to and from Schiphol are exempted but if you want to go to Lelystad or points North or East, you have to fly around the ‘transponder prohibited zone’. It’s crazy. Let’s hope the same thing doesn’t happen in the UK when Mode-S becomes mandatory.
More information (in English): AIP SUP 04/09.