Cees, in my opinion the biggest suspect is lack of space in BD50 replication for Q3, but that still doesn't excuse not just putting the film with minimal extras and lossless audio on a BD25. When all the other studios show that it can be done without hampering the PQ, there's not a lot of reason...
It depends on the source of the criticism. A guy like Robert Harris has the background and the knowledge to be considered a reliable source on PQ issues, whereas you can generally discount your average LordSauron69 ranting and raving when his only point of reference is screenshots from DVD...